Restoring a 1973 BMW R75/5 Motorcycle

September 2, 2007

Butterflies are free

Filed under: /5, 1973, airhead, BMW, BMW motorcycle, motorcycle, motorcycle restoration, R75, R75/5, SWB — Penforhire @ 9:52 am

Or as Brad suggested, “Dr. Leaky, I presume?” At the end of this holiday weekend we complete our long journey. Labor Day, how appropriate? Huzzah for the Knights of Labor!

Have you ever had the experience of wrenching on something you worked on earlier and, seeing incorrect assembly, thinking you couldn’t possibly have been THAT inept? I get that a lot. Like “what blind brain-damaged one-armed monkey assembled this?” Oh, right. Me.

You may recall carb rebuilds were the very first thing I did, even before I learned how to post full-size photos here. I always understood the basic principles of how a carburetor works but the gap between basic principles and understanding specific functions of each carb part is huge.

There is still an “official” Bing agency in the US ( I need to order their inexpensive CV tuning guide since everyone recommends it but I’m far from fine tuning yet. Oh yeah, they offer carb rebuild service — $180 for one, $322 for both, not including any special restoration like sandblasting. So they’re talking about installing the $50 twin rebuild kit (which is overpriced to start with for some o-rings, gaskets, and diaphragms) for $322? What a ripoff! And, of course, you can buy a new Bing CV carb for $465. Ouch! Rocky Point Cycle sells a Mikuni carb retrofit kit for $375 (for the pair!). Many 5-owners swear by it. Funny because without even mentioning this to Brad he mentioned dirt racers also swap in Mikunis for Bings with some regularity. They give better acceleration and throttle response at the price of reduced gas mileage. But I want the stock Bing look and I’m not ready to be beaten by my carbs!

So I’m determined to fix whatever ails my old carbs. I took off the left carb to work on it properly on the bench. I even have, as a guide, Joe’s pair of assembled carbs that he says are in working order. The very first thing I see is something I was expecting. I did not install the butterfly correctly. There is a chamfered edge that allows it to seal tightly against the carburetor. I installed it backwards and left a gap to the carb walls.


This may or may not be my only problem with idle. According to the archives at 5 United it is sufficient to cause impossible tuning issues. All better now —


I continued to tear the carb completely down. Hmm, the internal choke assembly was 180-degrees reversed (compared to Joe’s). Smooth! No idea if that affects idle but it’d sure affect the enrichener. Some yellowish bits of something like plastic are in the main carb body —


I had soaked the body in carb cleaner back when but now I attacked it with spray cleaner. Wear goggles if you do this because the spray comes out of the carb in unexpected ways. Just because all current sprays are reformulated to be environmentally safer doesn’t mean they won’t harm you. The ingredients mention acetone, alcohol, toluene, and methyl ethyl ketone (MEK). Stay away from sparks or open flames too!

The diaphragm-driven slide (moves main jet needle up and down) felt reasonably smooth but I wasn’t taking any chances. I could feel where slight corrosion might hang up the larger base where it slides against the carb body. I sanded the carb and the needle base with a series of sandpaper grits — 1000, 1500, and 2000. Then I used the 2000 grit on the smaller polished slide-tube and the female tube of the carb top. When I was done the assembled slide felt more free to move.

I took some of that fine sandpaper and worked on the idle air mix screw. It has a pointly metal tip and I noticed some slight corrosion on it.

I might end up replacing the main jet needle but I cleaned it up and reused it. The archive knowledge says these are wear items that should be replaced between 30K and 50K miles. The symptom is worse gas mileage. I should get somewhere north of 40 MPG and possibly over 50 MPG! There are four needle adjust positions in the slide. If it sticks out more, or “drops,” it stays more in the way of gas flow and leans the mixture. The book position is the 3rd notch or 38.5 mm sticking out from the slide base (best way to check since the notches are hidden).

If you ride for days at high altitude, some say > 5,000 feet, you want to drop the needle one notch (2 mm) because thinner air richens the mixture. Even though air volume is constant in a CV carb the oxygen content drops. I think I could do this in less than 15 minutes now (you only need take the tops off the carbs).

I had to replace a few more o-rings I damaged. They just don’t stand up well to removal and installation stress. I think I figured a way to improve that situation with a light coating of synthetic grease on them prior to installation.

On the right side carb, a miracle, the butterfly was correctly installed. However the choke guts were 180-degrees wrong and the main jet needle was off. I’m glad I stumbled across that 38.5 mm dimension because if you are fumble-fingered, like me, the hidden-notch system for setting the needle lacks surety. But whip out a caliper and you’ll know beyond any doubt which 2 mm increment you’re snapped into. I moved the float position slightly (to eyeball-level engagement with the carb body, like the book says). I didn’t spot anything else wrong on the right side but I polished up the slide areas.

Of course I had to wrestle with those intake elbows again.


I did not know the left and right are different. Fear not, it is truly impossible to mount them backwards. I know because I tried. The angle is significantly different because the two cylinders are offset an inch or two even though the air filter connections are dead even. My right side elbow fits reasonably well but the left side elbow seats on the air filter connection at a little too much angle, as if the engine or air box is not sitting in exactly the right spot in the frame. When I was done I sprayed every junction with carb cleaner while idling and did not detect any change in RPM.

Snowbum is adamant that you have to warm the bike up with a real ride, say ten miles, before any carb sync will be accurate. Nevertheless we have to start somewhere. I warmed it up in the garage with a powerful fan running air across the cylinders. Hey, it seemed to start easier and the chokes do something now! I first played by ear, adjusting the idle air mix for maximum RPM and getting the throttle stops to idle near 1000 RPM. Gee, starts even easier! Then I whipped out my Morgan Carbtune again and this time it worked. Note it has to be flipped upside down , as printed in their instructions, to read the low vacuum (they say around 8 cm Hg) of a BMW boxer engine. I was pretty close to max idle mix vacuum on each cylinder by ear. After a couple of adjustments I then balanced the left and right throttle stop screws for equal vacuum while idling near 1000 RPM. Those weren’t quite as close.

From all my reading it seems best to idle a little high rather than low because the oil pump doesn’t generate enough pressure at or below 800 RPM. It might be my imagination but I could swear the mirrors don’t shake as much now that I got an initial sync. The throttle cables are roughly synced, same 2 mm slack in the cable, measured by tugging on the cable fitting right above the carb.

Shall we? Let’s.

I rode it around my block once more to make sure everything was still traffic worthy. Yep. Clutch engagement still needs coarse adjustment. Front brake is grabbing better though the rear is still too soft (pedal engages a bit low but any higher and the brake drags). Off to the gas station for a full tank of petrol. Feels a little spooky moving around in traffic. I’m being gentle and avoiding high revs so I feel a little crippled and defensive. 3rd gear runs smoothly. I ride a larger loop on my way home, barely hit 4th gear just to check it, and when I stop I notice the idle has risen to 2000 RPM. I’ve gone a total of five miles and I pull in to the garage to immediately check carb sync again. It did shift a little, now that it is properly warm. The right carb throttle stop is a bit sensitive. A quarter-turn near proper idle makes a 500+ RPM difference.

I’m a little concerned about the left side idle air mixture screw. The maximum vacuum point is not as sharply defined as it is on the right carb. Makes me think I have a leak, maybe around the needle’s o-ring? I’ll have to check it again later. But it does have an effect if I screw it too far in or out (loses more RPM than actual vacuum change).

Let me say a few things about riding this machine. After only that short jaunt it stands in stark contrast to my ’05 Yamaha FJR. I guess modern motorcycles snuck up on me. I’ve had seven different bikes over the years, each usually newer and more powerful than the last (excluding a short-lived move to a vintage Honda CX500 turbo). On the /5 there is a tremendous sense of riding something mechanical. There are all sorts of noises and vibrations. The control responses are ponderous. My FJR’s silky smooth controls, engine, suspension, and wind protection make the /5 seem agricultural by comparison. That sense is probably what the Harley community talks about and desires. I’ll admit it has a certain charm but I can see how my FJR makes the ride easier, much more of a magic carpet than a tractor. I hope Joe can wait for me at turns if we take the /5! I’d say the /5 will be easier for commute duty but even there the FJR’s ABS brakes can be a life-saver. I can see how I need to flip a mental switch to ride the /5 safely, increasing my space cushion and dealing with slower reaction speed.

I know how the rider is such a big part of the equation. And I know I’m a mediocre rider (took MSF Advanced Rider training but zero track time). But if you put Wayne Rainey or Mike Hailwood on my /5 (before Wayne crashed out or Mike died in a traffic accident, wise guy) and put me on my FJR I say I can dust them around the Isle of Man or old Nurburgring.

Okay so I’m staring at the beast in the garage and I notice a small drip of oil. Something I noticed last time I parked it after going around the block on it.


Time to investigate. As near as I can tell, this is driveshaft oil dripping from the rubber boot at the tranny. Here’s a view from under the bike.


You can maybe see the oil weeping under the rear hose clamp. Some genius, guess who, set that clamp such that its screw cannot be accessed while the battery is in place. After pulling the battery and loosening to rotate it for future access, I tightened it as much as possible (clamp ends touch) and we’ll see if the oiling diminishes. Swingarm oil level is hard to measure accurately. You just stick a post or screw driver in there and look at the depth of oil on it, give or take a mm.

I think I have another oil leak, one tiny drip after running, weeping at one of the studs at the top of the tranny (right at one nut).


This is only a drop or two a day when run and there is not even a hint of the oil level dropping in the tranny. That nut is as tight as can be and I never pulled the rear cover off the tranny. It might just be the same drive shaft oil leak flying around. We’ll just keep an eye on this one.

Hmm, now that I think I’ve got some more stars in alignment how about a longer ride? Let’s go down to my closest dealer, Irv Seaver BMW. We’re in the middle of a heat wave so I put my mesh gear on and off we go. I’m taking surface streets to vary my RPM and keep it under 4K. First thing I notice is my idle RPM is way up again after ten miles or so. Grrr. Second thing I notice is my clutch engagement is shifting a little toward the end of lever travel! I end up taking it real easy at the lights because the clutch spun up twice when I tried to accelerate hard from a stop (that sure gets your attention in traffic!). The hand lever adjustment is a fine tuning, not coarse enough. I was sweating that one because while I have the BMW toolkit with me I’m not dead sure I had the necessary 10 & 14 mm wrenches to make a clutch adjustment (later confirmed they’re in there). Front brake is working great but the rear is still only a suggestion of a brake.

I’m glad I’m wearing full boots because I feel annoying heat at both ankles from the engine (while ambient is nearing 100 degrees). I’m thinking this will be more fun in cooler weather. Total heat is slightly less than my FJR but it moved from my crotch to my ankles, an extra improvement!

By the time I get to Irv’s my right hand is telling me a Throttle Rocker is a great idea so I buy one. I dislike the new velcro style (Cramp Buster has the molded one-piece patent) but it works. I roll around on the ground to do a blind adjustment of the throttle stops to lower idle a bit. On the way home I do a little highway time. Los Angeles area traffic is thick enough to guarantee varied RPM even on a highway. I get up to 75 MPH indicated and then back down for a short cruise at 65 MPH (just under 4K RPM in 4th gear). I can feel the engine has plenty more to give, I’m nowhere near full throttle, and I believe this bike will do the ton. Just not with me at the helm! Carburation between 2K and 4K RPM is great. Quite responsive. The front end feels fine, not a hint of wobble at any speed or change in speed so far. The front suspension & tire combo doesn’t like rain grooves in the direction of travel, dancing much more than I like, but nothing hazardous. Chalk it up to feeling the road nicely.

When I pull into the garage I’ve gone 35 miles or so. And I’m dripping a new fluid! I was careful to examine the ground when I stopped at Irv’s and nothing was leaking there. I’m pretty sure it is fork oil from the left leg based on its low viscosity along with where I’m getting fluid. I think it is squirting out under fork compression but I haven’t seen it in action yet. Nothing dripping while it is on the centerstand. It got on the left side of the front fender, a little on the left sidewall of the front tire (scary!), and a light spray on the ground where I brake to make a 3-point turnaround in the driveway to back into the garage. The top and bottom of both forks seem dry so I’m thinking it must be the shaft seal under the gaitor. That’s a new seal (see photos in a much earlier post). I hope it just popped out or ?

While the bike is still hot I immediately hook up the Carbtune and re-balance the carbs. The right side idle is more sensitive than the left but I get everything looking right and near 1K idle. The air mix screws needed no changes, only the throttle stops. When the idle was racing I double-checked the throttle cables for slack and they are fine. I let the bike, and me, cool down before I start wrenching elsewhere.

I lift the right fork boot and, what-do-you-know, some fork oil pours out and I see this.


Is my mechanic’s intuition working or what? From here it looks like part of the seal was torn off and the built-in compression spring is tweaked in a few spots. You know, just an hour ago I was at Irv Seaver BMW. *Sigh*. I call to make sure they have this seal in stock & to set it aside for me, jump in the car, and drive. Hmm, temperature is a few degrees over 100 now. All this for a $5.75 ($6.20 with tax) part! I joke with the parts guy that I’d pay more if he put it in for me. He says he’d charge a whole lot more for it.

After I drain the oil, remove the front wheel, remove the fork brace, and disconnect the fender I remove the lower fork leg.


Hmm, it didn’t exactly eat the seal. It folded over at that point. Strange. I check the upper fork leg and it feels smooth. I’m thinking maybe the bike knows I close to the end of major wrenching and doesn’t like it.

Here’s the oil I recovered.


That looks like virgin oil. No darkening or bits of anything in it. I recovered 230 ml so that means the seal blew out 50 ml. I reuse the recovered oil and load 280 total back through the top of the fork. Did you know that oil fill cap is hard to access while the handlebar is mounted?

I want to check all my work and try another ride but it is so hot I’m wilted. I sit around in my air conditioning for a few hours, contributing to the possibility of rolling blackouts because our power companies can’t plan for shit but they sure know how to rake in the money. And I eventually suck it up enough to go for another ride in the oven. Hey the full-choke start worked this time but I had to immediately (started to die) go to half-choke for a few seconds and then hold throttle against no choke (engine sputtering again) for a minute to warm it up. I go about seven miles this time. As I pull in the driveway I don’t see any fluids leaking. That’s a first. Hoo-rah! Clutch adjustment is just right. Throttle springs are still too strong, gotta give the throttle a he-man twist. Can’t wait to finish break-in because the engine is just coming alive at 4K RPM. Idle RPM after warm-up is still pissing me off because it is high. I attack the throttle stop screws again but they sure are sensitive.

At this point I estimate I have somewhere around 375 hours of labor in this project, which started in December 2006 and ran to now, the end of August 2007. I did not keep as faithful tracking of my time as of the money. I never worked on it less than 10 hours per week (every weekend, some nights) and often exceeded 16 hours. A more competent wrench could probably cut that time in half but he’d charge way more than me. It was funny how I had all the patience in the world for eight months but when I caught a whiff of the end I fell into a frenzied effort for about a month to get ‘er done. I was ready to bust if I couldn’t get on it and ride.

So what else is left to do?

The oil pressure lamp still never lights. I need to double-check but I think the switch is grounding properly with the motor off so it is in the harness or the bulb. If I go into the headlight bucket to look I should also add a hose-clamp strap around Stan’s ignition key cylinder to be 100% sure it will never rotate.

I still need to replace the horn. I’m thinking to wait until I have to take the tank off for something else. Not only would horn access be easier but I have a hankering to go for a much larger horn like the Stebel Nautilus Compact (134 dB! 18+ Amp draw!) and I’ll have to run a new relay direct to the battery, triggered by the OEM horn switch.

I want to increase the wire gage of the accessory power line I added. Right now it has a 3 Amp rating, enough for my Battery Tender to charge but not really enough for a Gerbings electric liner & gloves.

I have to finish break-in (say 900 miles), change all fluids, and perform another valve adjust.

There are a raft of other items like new shiny yellow steering head reflectors, Hepco & Becker saddle bags, and some Rok Strap bungee cords. But I don’t consider those actual fix-it tasks.

I need to find the perfect location to take some high quality photographs. I have it in my mind to ride to the San Joaquin Valley National Cemetery in Gustine CA where my dad is buried but that’s a seriously long ride, about seven hours each way, and I have to be uber-confident in the Blue Baron first. Here are a couple of documentary images. The link below each image will open a big JPEG file ready to run through a typical ink jet printer at 10 inches wide (rotate them or print in Landscape mode). They are around 1 MB in size so if you’re on a slow connection you have been warned. You may use these images in any non-commercial application as long as you attribute them to this blog.





You guys are welcome to stick around but I expect to taper off my postings unless something blows up in the next week or two. I will leave this blog as a /5 resource for as long as WordPress will host it. Even with anti-spam software I have to constantly weed junk-comments here so the weeds may linger longer.

Now that I’m feeling my oats I’m considering a go at restoring my father-in-law’s early 1960’s Jaguar E-Type (XK-E), a series one and possibly one of the earliest “flat floors.” I need to dig it out to evaluate it. He bought it new but it sat in his garage for decades after a crash. I’m sort of doubting I’ll have the energy to run a similar blog on it and the economics make it a multi-year proposition… or “foolish” to summarize. Too much hubris. But you never know. The photos and text in this blog were helpful to have for my own assembly. But it adds hours each week to do. I’ll leave you with some old English car jokes, sure to warm the hearts of BMW airhead enthusiasts —

Why do the English like warm beer? Because Lucas made their fridges.
Lucas denies having invented darkness but they still lay claim to sudden unexpected darkness.
The Lucas motto? “Get home before dark.”

Thanks for coming along on the ride!
Eric Arnold


August 26, 2007

Improvise. Adapt. Overcome.

Filed under: 1973, airhead, BMW, BMW motorcycle, motorcycle, motorcycle restoration, R75, R75/5, restoration — Penforhire @ 4:16 pm

And in the end, surrender.

Joe spotted a big error in my costs from the last post. The third item, wheel work for $594, is counted twice, once as that lump sum and then again spread out into the parts and labor. So that total is more like $8600. Joe says I really do need an accountant.

Since last week I retorqued the heads, gapped the valves, cleaned the carbs again, added clear in-line fuel filters to each side, discovered the horn I worked so hard to clean is kaput, and then came the big puzzle — adding the Boyer Microdigital ignition. One reason I got it started with the OEM points system is I can switch back to the stock system in maybe 30 minutes if it fails on the road. It was important to know it worked.

Here are the Boyer rotor & stator mounted in place of the points.


The stator has two coils epoxied in place 180 degrees apart. The rotor has a matching pair of magnets. When they rotate past the coils a voltage is generated. The stator plate rotates just like the stock points plate to adjust timing. The advance curve is built into the Boyer and is not adjustable. I believe it is a little slower advance than the stock curve, hitting full advance at 4K RPM where the OEM weight system hits maximum near 3K RPM.

Here is the recommended spot to mount the Boyer brain.


This is just behind the coils and in front of the tool box, strapped in place with tie wraps (provided in the kit). You can see a laminated schematic (from Prospero’s Garage) rolled up and slipped into the frame tube under the tank. Seems like a good place to keep it.

Oh, the Boyer instructions were simple enough but after I wired it up I had the strangest problem. The starter would only turn over for a second or so. I’d have to turn the ignition off and on again to get another second of cranking. It was as if the starter relay was opening. I was going nuts trying to figure it out. If I removed the Boyer’s black wire to the coils it’d turn over fine but I had no spark. If I removed the unnecessary wire from the coil to the now-unused condenser the starter wouldn’t budge. The schematic told me something was way wrong since that condenser lin is an isolated run.

Well, I could have sworn I used my ohm-meter to confirm that condenser line was what I thought it was but I’d have been wrong. Double-checking my assumptions, I found that black wire was actually the voltage sense line going to the Enduralast regulator. I had hooked it to a coil for switched power. So I moved it to an open switched-power lug on the starter relay and everything was peachy. I had as much starter as I needed and the ignition started the bike with minimum fuss. Woo-hoo!

I sent a help e-mail to Stan and I posted my trouble on the 5 United board. So then I had to fess up and tell everyone I was an idiot and how I solved the problem.

Next I grab my trusty timing light to set the timing on the Boyer. I haven’t used my timing light in over a decade and it is, um, not so trusty. No blinky-blinky. I pop it open to look at the circuitry but considering how I did with the Boyer ignition I know I’m just fooling myself. I don’t see any blown fuses or crispy black spots and it was as cheap a light as one could buy back then so I went out to buy a new trusty timing light. Blinky-blinky.

I had set the stator plate midway in its adjustment range and this turned out to be slightly retarded at idle (“S” mark). So naturally my first adjustment overshot the other way. Boy is that adjustment sensitive! I got it close to centered. I saw some odd jumping of the timing mark but that could be due to too many things. The Boyer instructions only mention checking for full advance at 4K RPM. I haven’t broken in the new engine parts yet so I only briefly took it to 4K and observed the “F” mark centered just right. I could also see it moving smoothly up and then down again as the throttle was adjusted. That’s good to go.

I tried balancing the carbs beyond the crude adjustments Joe and I did before but something is not right. I’ve got a Morgan Carbtune (non-mercury carb sticks) that I use to balance the four cylinders of my FJR. Nothing is as smooth to watch as mercury but this does the job. So I hooked ’em up to the Bing vacuum ports, normally sealed with a screw-and-fiber washer. Another odd thing happens. I get tons of vacuum on one carb and zero on the other! Since I know both carbs are working (heat in the headers & idle moves with either throttle adjust) that means the port is somehow blocked in one carb. I blow through the port and I can hear my compressed air blowing into the body of the carb. Still zero vacuum. I swap Carbtune lines just to be sure it is not the gauge. Grrr. By the way, the carb that shows vacuum maxes out my gauge at 42. I think that is supposed to represent inches of mercury but absolute values are not important when you’re balancing.

I’m also experiencing other odd carb behavior where the idle will rise to 2k or more for ten to thirty seconds, or stick there after goosing the throttle, then drop back down. I’ve got the throttle stops at lowest idle point just above dying, around 800 RPM. Lacking the vacuum port access to balance the carbs I will have to resort to the older cruder method of running the engine on one cylinder at a time, maximizing idle-screw-adjust RPM, and then setting the idle throttle stop. I am a little hesitant because of the Boyer ignition. I believe I will have to rig up a solid grounding clip for whever plug is out of the engine but I need to do some research to make sure.

It idles and revs good enough to work out some kinks on the road so I move on to the front brake which is way out of adjustment. Here is the front arm.


The arrow shows one of two sets of punch marks I added to the arm before I took everything apart. You can see I put it together just the way it came apart. But it was clear to me that the front arm angle was incorrect. There was no adjustment range and the brake shoe was already touching the drum. So I pulled it off and moved it one tooth clockwise, increasing the range of adjustment. That made it trivial to remount the brake cable. The threaded rod now fell fully through the arm with no extra effort. Some of you probably wondered about all my struggles and now I know why. But getting this arm angle right exposed my next problem.

Yes, despite clear instructions and conscious attempts to follow those instructions I somehow loaded the two brake springs backwards. Or so I thought. The symptom was the front arm moving the shoe to the drum before starting the rear arm. The rear spring is supposed to be weaker so that is the opposite of what is supposed to happen. Grrr. I call Joe to whine about it and maybe prime him for spring-assistance (again). He’s up to his hips and fully occupied by multiple toilet replacements. Hmm, since he didn’t ask for my help maybe I’m getting the better end of this deal. I’ve done toilets before. So enough whining. Time to spin wrenches and sacrifice flesh.

Off comes the front wheel. You’ve seen this part before.


The good news is, I did not load the springs backwards. The bad news is, I used two of the same spring (both the stronger spring). Yeah, these don’t look the same in the photo do they? In fact, both are 2.5 mm diameter wire. The proper rear spring, which I had hidden away in a bag, is 2.3 mm diameter. You might not think 0.2 mm would make that much difference but it sure does! I struggled for a while to get the incorrect spring off before I pulled out my go-to tool, a cut-off wheel. Not like I was ever going to use that spring again, right? And the new spring was soft enough for me to grunt it on with vice grips and some body weight.


On goes the front wheel and the brake action is now correct. As I pull the brake lever the rear arm spreads the shoes until they touch the drum and then the front arm starts spreading. Yay!

The next trick is adjusting a little cam near the front arm so the arm has just 4 mm of motion (measured at the cable) between no-brakes and full-on. It is a pre-spreader for the front brake lever. What makes this tricky in my case is the interior-hex-head adjusting bolt was already rounded off by a mechanic that must have been denser as I am (is that possible?). You must pull the brake lever to remove pressure on that cam before making ANY adjustment. Otherwise the turning pressure is too great and, well, you round off the adjuster socket. When I hold the brake lever in I can spin the adjuster cam with my bare fingers. So why is this an issue? Because the lock nut on the adjuster wants to turn it slightly as I tighten it. So I pull the hand lever. Then I move the cam so it is right there, at the contact point. If I could tighten the lock nut here I’d have zero motion of the front arm. By the time I get the lock nut tightened it rotates the cam so I have maybe 7 mm of front arm motion before full-on braking. That means total brake lever travel is more than it needs to be, most of the the way to the handle before the brakes are fully engaged.

Adjusting the rear brake arm is easy. Just spin the adjuster on the end of the brake cable until the rear arm starting position is where you want it. The front brake arm isn’t going anywhere until the rear arm pushes its end of the shoes fully against the drums. So this adjustment is independent of the front arm adjust. I tried to make up for my overly-long front arm engagement by making the rear engagement as short as possible, and snugging up the brake control adjust at the handlebar, but you really want 4 mm of rear arm motion.

Another not-so-subtle point is maximum brake power (leverage) is obtained when the two brake arms are full-on at 90-degrees to the cable. In my case this is a go. The angles are good. Duane’s article on brakes is a good one and he says if you have any error you want the angle to be slightly more than 90 degrees (arms not moving quite enough) because as the brake wears and the arms move further you will gain leverage instead of losing it.

I have an idea to cut a short length off an Allen key and epoxy that into the rounded cam adjuster (happens to be a 4 mm socket). I think if I do that correctly I’ll be able to improve my front cam adjustment. Put that on the list of things to do.

Okay, here’s the decisive moment. Time for me to take this heap around the block and see if I have a motorcycle or just expensive antique mechanical art. The front engine cover is still off, you know about the front brake, … blah, blah, blah. I’ve got enough excuses to keep this beast in the garage for at least another eight hours of work. My insurance card just arrived in the mail so screw that, we’re going for a ride!

I air up the tires to my best-guess starting pressures (38/40 PSI) for my unknown tires. Inner tubes lose air a lot faster than my tubeless tires! I put on my best “pavement luge” outfit (boots, pants, jacket, gloves, helmet) because who knows what’ll happen. I hop on and roll it off the center stand. Geez, I don’t remember this bike being so tall! I’m barely on the balls of my feet. I work the side stand to get a feel for it while the bike is still cold and I’m calm. Geez, that’s a bear to operate — your left leg presses against the (hot) cylinder to complete its forward motion! I bounce on the seat and notice my rear suspension is too stiff. Maybe it’ll break in and I’ve got too much preload also. Heh, at my size that rarely happens! Deal with it later. Start the engine and paddle out onto the driveway. Look both ways and step into first gear while grabbing the front brake for all I’m worth. I’m not getting any of the jump I remember it had, going from neutral to first. Good vibrations.

I can’t remember being so nervous getting on a bike. I slowly ride it down the street and stop next to my two-houses-over neighbor Davis, getting the first feel of the brakes. I’m hearing a box-of-rocks noise when I move. I’m thinking tranny thoughts to myself, “that can’t be good.” Davis rides a recent Road King and a real-deal Triumph chopper. His HD’s modified exhaust is merely annoying. His chopper’s open pipes make my teeth feel loose. He gets a chuckle while helping me out. He says the engine sounds great but that box-of-rocks noise is probably my center stand, which is dragging along the ground. Yes, I rolled off the stand but forgot that I have to lift it up until the spring ‘cams’ over to hold it (unlike any of my other bikes). Rookie error. Well, I’d rather have brain fade as a cause for noise than an evil tranny.

So off I go around my cul-de-sac neighborhood. I’ve got a triangular loop with almost no traffic that is only 1/3rd of a mile. Not too far to push in case it dies, right? Gosh, the front end sure dives under braking and I do have to give the brake lever a he-man grab. Rear brake could be adjusted higher but it seems okay if I step on it hard enough. Clutch engagement is right at the end of travel, I’ll need to adjust it. I do one loop in first gear with a bunch of brake checks. The engine shudders slightly off idle as I feed it gas when I engage the clutch. Not too unexpected. That’s the big symptom of unbalanced carbs. Oh yeah, the handlebar pinch bolt for the clutch lever is slightly rounded (another internal hex socket) so it is not tight enough, so go gentle on the twisting there. Second loop I lift it into second for a short stretch but I’m instantly going too fast for the confidence I have in my brakes. Back to first and back in the garage. Onto side stand then center stand.

Phew! I had no idea my first ride would feel so traumatic. Can you believe I forgot to write down the mileage when I started? Now it says 72,592. I need to know this for break-in and fluid change purposes. I still have no idea if the speedometer works. I was so focused elsewhere on my little jaunt I forgot to look!

I later got the front brakes properly adjusted. Here is the relaxed position —

And the full-on position —

Okay, with the timing also settled it is time to get that front engine cover on. You may be wondering why I griped about it repeatedly in this blog. Well I found out why I was having abnormal difficulty. I think it is the Enduralast rotor frame. It must be slightly deeper than the stock rotor because it was just barely hanging up on a casting post inside the cover.


I could get the cover locating pin inserted or the bottom of the cover seated, but not both at the same time. Eventually I wore that little shiny spot in the cover trying and failing to get it on. Here is the rotor frame bolt I think I was hitting, though there is no matching mark I could find on the bolt head or frame.


The problem was solved by a little sanding on the offending casting post of the cover.


This is not a structural point, the rib that runs through it is still intact, so the cover should not be any weaker. The cover slipped right on, at least compared to the fruitless sweaty grunting that came before.

I made a trip to the hardware store, used an extractor to get the old clutch lever pinch bolt out, and replaced it with a nice $0.89 stainless bolt (6×1.00 mm by the way). I think someone got lazy in the past because the highbeam/lowbeam handlebar switch gets in the way of properly adjusting the pinch bolt. You have to remove it or else work the bolt at too much of an angle. Okay, clutch lever is a go and I moved the clutch engagement point more to my liking.

Now my sense is only two things still stand between me and the open road, my left and right Bing CV carburetors. I soldered an old spark plug electrode to a wire with an alligator clip on the other end to use as a grounding tool to balance the carbs using the “one-plug” method. But I never got far enough to use it. I let the bike warm up in the garage with a strong fan blowing air over the cylinders. No matter how I messed with the idle adjusts and throttle-stops I could not get a steady idle. It’d hold up between 2K and 3K RPM for a minute and then suddenly drop down and sputter. Left alone it would die. All with me doing nothing!

I dropped the float bowls. Nothing nasty floating in the gas. I pulled out the idle jet and idle adjust needle from both carbs. There was some o-ring damage that was easy enough to repair (see pics below). The orifices were clear. I blew everything out anyway.



It didn’t make any difference. My impression is the big issue is my left carb because that throttle-stop screw sometimes initiated wild swings in RPM (not always). I might have a sticky slide. There is still the complete lack of vacuum at the test port to consider. That port is supposed to be connected to the chamber after the butterfly, so at idle the piston’s sucking through the intake port against a mostly closed plate produces a theoretical 30″ of mercury (according to Snowbum’s tech article).

Maybe I’ve got a leak between the carb and the intake? I can try spraying brake cleaner (or WD-40) over the area while running. Sudden RPM change indicates a leak. Of course, I’ve got sudden RPM changes without any spraying and that collar is seated nicely. I can believe a small leak at the air box but that won’t affect idle like this. I think the next thing to do is to pull the slides and polish the surfaces. Maybe take the carbs apart completely again and try more cleaning. It is possible I put one or both butterflies back incorrectly. Beyond that I’m a bit mystified.

Oh, and not that it matters but if I use the choke I can’t get ‘er started. I have to crank it a bunch times and feed some gas with the throttle. Since the timing, valve adjust, plug gaps, and coils are good the many-cranks-to-start strongly suggests the carbs are misadjusted or faulty.

For tonight, I surrender.

August 19, 2007

It lives!

Filed under: /5, 1973, airhead, BMW, BMW motorcycle, motorcycle, motorcycle restoration, R75, R75/5 — Penforhire @ 2:43 pm

I was right about the chances of my poker hand holding up.


Now while I AM pleased to win, why couldn’t it have been one of the runs where the prize is a pair of new tires?! I shouldn’t complain. Not only is this a better trophy than the ink jet print-in-a-glass frame I got for my last win but I’m more likely to get a traffic ticket on one of these rides than win it.

Here are my Bing carbs.


Remember way back at the start of this adventure, how I spent all that time cleaning and rebuilding these? Funny but now the exteriors look too rough compared to the bike I’m mounting these on. I probably should have bead blasted these. I set all the jets to nominal starting positions based on the service manuals and leveled the floats. I have no idea if these carbs will work but we’ll find out soon.

Here’s the airbox outlet on one of Joe’ spare parts.


Hee’s that same outlet on my airbox.


Notice that I’m missing the o-ring that BMW must have designed on later bikes. Too bad because that looks like a good idea. It was a serious struggle to get the carbs mounted.


There is a rigid plastic elbow between the carb and the airbox and everything fits so tightly together. Why couldn’t BMW use something flexible there? If they didn’t like rubber then make it corrugated for flex, upsize it if you’re worried about air restriction. Oh yeah, even the BMW-specified hose clamps were a problem.


Looks nice, with that BMW logo, right? But the sizes were such that getting them each started over the coupling hoses was a finger-munching exercise, whether I slipped them on fromt he sides or opened them completely. I guess they didn’t want too much clamp free tail after tightening but this was just ridiculous. After my fingers were nearly useless (again) I used a couple of larger generic clamps on the left side.

After I got my clutch cable routed I tried to verify it was not binding. I was concerned because the pull required was studly. I recalled it always being stiff but I was worried about just how strong that spring tension felt. Joe assured me they really were absurdly stiff and folks rarely kept the clutch disengaged at stop lights. Darn thing felt like a hand exerciser! Well, that meant it was time to whip out the Easy Clutch from Bench Mark Works. I understand there are a variety of these devices but Craig Vechorik’s is what I think of first.


It is a straight-forward pulley system. If I remember my physics classes correctly it doubles the travel of the hand control, halves the effort, and halves the motion at the clutch. The issue is if the clutch engagement varies too much, say when it warms up or stretches, I may need to chase clutch adjustment. It didn’t feel right but I had to cut my brand new clutch cable back about 4″. The cut end gets inserted into the brass sleeve (seriously tight fit) and held with three set screws. I worry about those set screws but the cable pull should have half the tension on it that it had before.


Seems to work fine in the garage. Makes the clutch motion just stiff instead of “you’re shitting me, right?”

I mentioned some of the cosmetic parts are still rough on this bike but the tail reflector was bugging me so I splurged on a replacement. I still need to buy new headlight ears because of similar rust and dings I can’t improve enough.


Here is the ignition key kit from Stan at Rocky Point Cycle.


This is designed to completely replace the super-funky original switch but leave the bucket exterior stock look. It’ll also prevent anyone from starting the bike with just a 10 penny nail, as Joe related anecdotally.

The first piece is a collar that you wrap the original bucket tabs around.


Here’s the switch part, inserted into the collar and held with a set screw. As mentioned in the instructions, I had to grind the metal key opening larger, underneath the sliding plastic cover.


I should note that while the kit comes complete with some nice Posi-Lock connectors I was forced to use my own Posi-Lock stash because the OEM wires were too big to use Stan’s included parts for the ground and horn connections. All the remaining connections go to the new terminal block in this kit. By the way, this new terminal block is great. It uses a non-rotating clamp under a screw instead of the OEM bare set screws. If I have any trouble with the OEM block I’ll be looking to replace it with something like this.

Here’s a long shot of the bucket at this point.


And here’s a closer view of the messy spaghetti inside. I need an elf to come clean it up for me because if all my connections are good I’m not touching it.


Here’s an exterior view of the bucket and you can see how the ignition switch appears unmolested.


The key switch has three positions, extremely similar to the original switch, allowing the engine to run with or without the headlight.

Now I went to fit the gas tank and I discovered that not only is the wiring under the tank too messy but the EnDuraLast regulator/rectifier will NOT fit in the OEM location as planned. I had to move it foward and down.


By turning it 90-degrees it also made it easier to use just tie-wraps to secure it. I also had to extend the brown ground wire and use a new bolt-and-nut to ground its case. Then it was just a matter of making the wiring bundle a little tighter. I had to pull the speedo cable out of the tranny (again) to pass it on the other side of several wires. Then voila!


You might notice the stunning Keihan stainless exhaust pipes now mounted too! There is a small dimple on the left pipe but I can’t see sending ’em back to Stan because of it. We’ll see what he says.


The repair manual talks about removing the seat to remove or replace the gas tank. Nuts to that! It slides in place just fine with a little careful twist from the side. I need it to be easy to remove since I have to get back under there when I install the electronic ignition later. Here’s a teaser preview of those parts.


So now I’m down to just a couple of things that need doing before I try starting the bike. Technically I could try to start it but the headlight is not mounted to the bucket, two exhaust hangers are not secured to the engine/peg mounts, and the front brake cable is not mounted in the far arm. That’s it. When I got to tasting the finish last week it drove me to wrench harder after work this week, despite our local heat wave. I could hardly sleep, dreaming about getting it all done. Friday was my birthday and I took the day off to spend half with my wife (who works a 4 day/40 hour week) and half with this bike. I worked until I was completely spent, sore everywhere and filthy from rolling around the garage floor.

I’m frustrated by those three things left to do so I called Joe and begged him to come over this weekend whenever it was convenient to give me an hour of his time.

1) There must be a trick to the headlight ring that I’m not getting. It hooks at the top of the bucket and has a spring latch at the bottom. But seeing and doing are two different things.

2) I just need a little more muscle, two more hands, to push new springy exhaust hangers onto the engine/peg bolts. I can’t quite get a C-clamp to work in there.

3) The front brake cable is insane. I adjusted the cam spreader to its minimum but the forward arm is still just “a bridge too far.” Gary helped me wrestle with it last week and we got close but no cigar, maybe 1/8th inch away from starting the end-adjuster nut.

I just need to do those three items, fix whatever else I did wrong (probably some incorrect or poor crimps somewhere), do a checklist shortly after starting up (timing, balance carbs, re-torque head, valve adjust, fluids change, verify charging system), install the Boyer ignition, and bolting on the front cover. Hard to believe I’m THIS close to engine noise! I also got my first scratch in the paint. It is on the rear fender from the negative-side battery strap as I was yanking it into place. That won’t seem like much after the first time I drop the bike but right now it feels like a lot.

While I’m waiting for Joe to call I got a wild-hair idea. Idle hands and all that. I took the original key —


And I used a small Dremel abrasive bit to cut around the metal. After I cut away enough plastic (or glue?) I was able to pull out the bits —


Here’s the remaining plastic shell.


I was careful not to cut through to the other side and I was gentle pulling out the old key bits to avoid cracking the shell.

Here’s what one of the new keys looks like.


Yeah, I blurred the key code. Not that I don’t trust you guys but who knows who’s watching? I didn’t blur the key cuts because if you can reproduce this just by looking at the cuts then I’m not slowing you down much in any event, eh? Anyway, I went ahead and started grinding the head of one new key in a vice with a hand file until it fit properly in the old plastic shell. It took lots of back-and-forth test fitting in the ignition.

I mixed some 5-minute epoxy and poured it around the new key in the old shell.


If I did this right you won’t be able to tell I’m using a new key system when it is inserted in the bucket! How cool is that?

Okay, since Joe’s not on the way yet and to scare me straight, I promised you a better list of expenses. Here you go. These do not include any items under $3 and I probably missed a few items that belong on the list, say $100 or so. Also, I do not have saddlebags yet and if I go for new Hepco & Becker replicas they’ll cost me another $450. So we’re awfully close to a round $10K. Sorry about the formatting. I haven’t figured out how to properly insert a spreadsheet in a WordPress blog —

“Restoration expenses, 1973 BMW R75/5 in decending order
By item (smaller items not inc. tax or ship) Cost

Painting service (fenders & tank, with all prep) $835.00
Keihan /5 mufflers $595.00
Wheel lacing parts & service & tire mount service $594.00
EnDuraLast charging kit $469.00
Keihan 3-pc stainless headers $385.00
Pistons & rings (overbore set of 2) $358.00
Speedo & tach restoration service $353.74
Sargent Classic seat $319.90
Complete valve job labor $295.00
Tires & tubes $254.00
H4 headlight conversion $249.95
Rear shocks, Progressive (2) w/springs installed $249.95
Powder coating service $225.00
Stainless bolt kit $185.00
Boyer Microdigital electronic ignition $179.95
Centerstand $175.00
Rubber kit (hand grips, foot grips, etc.) $166.50
Valves (intake & exhaust, 4 total) $155.40
Polished spoke& nipple kit, front wheel $135.00
Polished spoke & nipple kit, rear wheel $135.00
Clutch plate $103.95
Lace & true front wheel $97.00
Lace & true rear wheel $97.00
EZ Clutch $95.00
Bore & hone cylinders (2) $92.00
Handlebar switch, left $90.85
Handlebar switch, right $90.85
Head exhaust thread repair $90.00
Tank emblems (2) $85.90
Ignition coil $77.39
Ignition coil $77.39
Progressive fork springs $69.95
Battery $68.00
Lock set (steering head & seat) $65.00
Hub cap $63.91
Main wiring harness $61.95
Starter relay $54.39
Wrist pins, lightened (2) $52.00
Beadblast cylinders & heads $50.00
Front end (forks) rebuild kit $49.95
Engine wiring harness $48.59
Top end gasket kit $48.00
Tune up kit (plugs, filters, gaskets) $45.90
Carb rebuild kit $45.00
POR-15 gas tank repair kit $42.50
Speedometer cable $40.39
Tachometer cable $40.39
Ignition switch kit (Stan’s) $39.95
Clutch diaphragm spring $39.59
Exhaust clamp rings (2+2), fit on headers” $39.56
Fuel petcock $36.25
Muffler brackets, stainless $34.48
Front seat hinge $34.39
Valve springs $31.60
Exhaust hangers, stainless $29.90
Mount front tire & tube $27.00
Mount rear tire & tube $27.00
Clutch cable $26.10
Wheel/swing arm bearing BR30203 $25.88
Wheel/swing arm bearing BR30203 $25.88
Wheel/swing arm bearing BR30203 $25.88
Wheel/swing arm bearing BR30203 $25.88
Bearing BR32 (steering) $24.44
Bearing, steering $23.95
Front brake cable $23.95
Wheel seals (2) $23.90
Wheel seals (2) $23.90
Throwout bearing (ball cage) $23.77
VIN plate & rivets $21.25
Valve seats $20.00
Fuel line (2 meters) $19.90
Wheel seals (2) $16.94
Battery straps (2) $16.80
Starter rebuild kit $16.80
Throttle cable $16.39
Wheel bearing (extra BR30203, other vendor) $16.10
Wheel/swing arm bearing $16.10
Wheel/swing arm bearing $16.10
Wheel/swing arm bearing, extra (destroyed one) $16.10
Spark plug wires, 5 K-ohm $15.95
Throttle cable, for USA bar $14.95
Turn signal flasher $12.95
BMW Microlube (clutch spline lube) $12.39
Gas cap gasket $12.19
Fork oil $11.99
Flywheel bolts (5) $11.00
Choke cable LH $9.59
Choke cable RH $9.59
Alternator rotor bolt $9.39
Push rod seals (4) $8.80
Timing advance spring set $8.50
Hand control perch (wedge) $8.10
Turn signal gaskets (4) $8.00
Driveshaft boot $7.85
Oil pan gasket $7.25
Hypoid gear oil $6.82
Swing arm seals $6.40
Driveshaft bolts (4) $5.80
Tach drive seal $5.70
Turn signal bulbs (4) $5.56
Clutch rod seal $5.00
Clutch rod felt $4.55
Front tank support (rubber) $4.39
Brake spring $3.20

Total $9,180.28

“I know what you’re thinking. Did he fire six shots or only five? Well, to tell you the truth, in all this excitement I kind of lost track myself.” Sounds like Dirty Harry was my accountant on this project.

The work continued because Joe stopped by! Yes, those exhaust hangers were really a two-man job. My new headlight needed a small tweak in the chrome ring before it would pop on. And the front brake cable had to be re-routed. Joe agreed the set-up looked right to have the cable loop to the left of the bucket and mount the gromet on the headlight ear’s clip. However that was just not going to work. Maybe my cable is not for the USA bars (it is same length as the old one). Who knows. We routed the cable to the right of the bucket and straight down. That gave us more play in the cable and it wasn’t such an absurd effort to get the adjusting nut onto the brake arm.

Joe didn’t like the amount of tension in the throttle so we re-routed the left side cable for less of a tight bend beneath the handlebars. Funny thing, that didn’t change the tension much. Must be those new throttle return springs I put on the carbs. More manly-man controls! He much approved of the Easy Clutch, and he helped me adjust it too (I didn’t have the clutch 100% engaging).

The moment of truth was upon us. I put a gallon of fresh premium gasoline in the tank. First time it was wet since the teardown. We set the petcocks to Reserve and turned the ignition key for the very first time. Headlight, check. High beam check. Tail light, check. Turn signals, check. Brake light, both switches, check. Instrument lights, all working except the oil pressure warning light. Either a bad switch or a bad connection (should light up until pressure is made) – deal with it later. Hold our breath and punch the starter button.

Nothing. Try a few more times because we’re stubborn. Nothing. I suspect the starter relay because my sense of wiring that was weak. Off comes the gas tank and Joe helps me re-wire that relay using the old one as a guide. There were some terminal # markings on the old one that are not present on the new relay. We try the starter, gas tank still off and plug wires disconnected. “Rarrarrarrarr!” Huzzah, it spins! Put the tank back on, turn the gas back on, reconnect the plugs.

“Rarrarrarrarr!” “Rarrarrarrarr!” Hmm, the starter is spinning the motor but no hint of ignition. Okay, pull one plug off and look for spark. Hmm, no spark. Well I did have the points wide open like the book said. No, Joe says we need closer to the right gap. So I twist the points closer, still not to book gap, and we get spark. “Rarrarrarrarr!” “Rarrarrarrarr!”

Hmm, “do you smell any gas?” “No, how about you?” And the spark plugs are not wet at all. Okay, so we pull off the valve covers and check the valve adjustment, not precise, just making sure we have some gap. Joe says loose noisy valves are less of a problem than tight valves that never close. Nope, gap seems about right and Joe turns the engine while covering the plug holes with fingers. Yep, we have compression (and Joe gets my anti-seize blown all over his hands). “Rarrarrarrarr!” “Rarrarrarrarr!” Nothing.

It could be bad timing but it’d have to be WAY out and I don’t think that’s possible. I never messed with the timing chain. We pull the float bowls off the carbs. Yep, we’ve got gas. But there is some fine gunk floating around in there. Joe removes one of the main jets, doable from below with carbs still on the bike. Ahh. Clogged. I scrounge for fine wire and come up with a set of pin-drill bits. He cleans jets on both sides until we’re satisfied that they are clear. He also noted they were loose in the carbs to start with. Odd, but then again I was the one who renovated the carbs. Slap everything back together.

“Rarrarrarrarr! P-too!” “Rarrarrarrarr! P-too!” Hey, it sort of wants to catch. One of the exhaust headers is warmer than the other so we were only sort-of firing one cylinder. Joe decides we should properly gap the points since they’re still way over spec. He shows me how to bend the feeler gauges to access the points more smoothly and we set a proper gap.

“Rarrarrarrarr! Vroom! Put-put-put-put-put-put…” I can’t believe it. It lives! Joe rolls back and forth under the carbs, first setting the idle adjust screws for max RPM (like it says in the book) and then setting the throttle adjust screws for actual idle speed (800-1,000 RPM). We jump for joy.

Joe calls his wife Mary. She must be out working in her garden so he leaves her a voicemail with the sound of an idling R-bike. I call Gary and make him listen to the engine purring. Joe’s got to go but his work here is done. I said I only needed an hour of his time. More like four hours.

Sorry I don’t have any photos to show of us leaping around the garage but we were busy! I’ve still got a load of things to do (mentioned way up above) before I hit the road. I’d say I’ll be scaring pedestrians next weekend. I’m too burnt now to do much more unless it cools off today (fat chance). I need to drain the carb float bowls again and I may need to clean jets again. I hope this is just form the first splash of gas through the tank but it is possible the POR-15 kit didn’t do the trick properly. I should add see-though gas line filters ASAP just to head off any future issues. Someone on the Airheads list mentions NAPA P/N 7-02323 or 7-02357 both fit the OEM gas lines.

Turns out to have been a good idea to wait on installing the electronic ignition because otherwise our troubleshooting would have been confounded by the little black box. Points certainly are easier to mess with. Now I can make the swap, knowing for sure the OEM system works.

It lives!

August 14, 2007

Technical difficulties

Filed under: R75/5 — Penforhire @ 7:03 am

The WordPress support staff tells me they are having a problem with the usual link at the bottom of this page that allows you to look at earlier pages of my blog. I got some questions about this from new readers. There are many prior pages (I’ve been working on this since December last year) but you cannot access them until the issue is resolved. Sorry for the glitch.

Keep checking for that link to appear at the bottom of this page.

August 12, 2007

So close yet so far

Filed under: /5, 1973, airhead, BMW, BMW motorcycle, motorcycle, motorcycle restoration, R75, R75/5, restoration — Penforhire @ 2:36 pm

There are a couple of other benefits to the Enduralast charging system that I forgot to mention. If the charging light in the instrument panel burns out it normally causes a charging failure since that current, through the lamp, somehow energizes the OEM stator system. The Enduralast system doesn’t care about that lamp. The second thing is normally you MUST take all ground lines off the battery every time you remove the engine front cover. There is too much risk of shorting a “hot” surface to ground when you move that front cover around. It is still a good idea with the Enduralast system but the stator shell is now grounded and there are no slip rings so touching the rotor area with the cover is safer.

Right, picking up where I left off last week, still installing the electrical system. Look, new Bosch coils!


At first I didn’t understand why there is a ridge at the lip of that hole you can see in the clamp. It is a grounding burr that makes better contact to the coil body. The coils are used for several chassis grounds and very high voltage is developed inside the coils. I was careful to grind off the powder coating where the top of the clamps are screwed to the frame. You want a good chassis ground. Any the brown wires you see on this bike are ground wires.

I figured I’d show you some of the steps used to ground the regulator/rectifier, for anyone out there less electrically inclined than even me. Here’s the wire with insulation stripped off the end.


Here’s a ring terminal crimped onto that wire.


This style of terminal has a plastic sleeve covering the whole area but I should have cut it away and soldered the joint in addition to crimping. I’m afraid that idea came to me after making many crimp joints so I will just live with fixing them as needed. A good crimp lasts for years but crimp-and-solder is even better. Of course I’m not convinced my crimps are that good to start with. I do add “dielectric grease” in every joint I can. That keeps out water and reduces corrosion in crimp or spade contacts. Wherever possible I add heat shrink tubing.


This serves several purposes. It keeps out water, adds mechanical strength & stress relief, and provides better electrical isolation from nearby metal surfaces. You have to think ahead with heat shrink tubing because usually you can’t fit it over the terminal when you’re done. If it is that big it won’t shrink to a tight fit down on the wire. Sometimes I use stepped pieces of tubing on larger terminals to still get a shrink to the wire diameter.

Here’s that Enduralast ground wire placed under one of the coil clamp screws.


Note the bare connector is an OEM harness ground and, in general, grounds don’t require electrical shielding. You have to worry more about any other electrical wire touching any grounded metal by accident. If you have a forest of closely-spaced terminals, such as at the starter relay, it is a good idea to have an insulator around every terminal, just like the OEM harness.

Here are two hot leads from the stator coils.


It doesn’t feel right but you have to cut off the original connectors on the Enduralast components, that white connector from the coils and a SAE connector (just out of picture) on the rectifier/regular line. Here is the finished set of Posi-Lock connections.


The red wire below is the battery lead to the regulator/rectifier. I laid it roughly along the path I intend but it is not properly tie wrapped in place yet.


Here are the last two Enduralast connections.


I took switched power from the ignition coils (at least I think that’s switched power). The white connection is a male spade to the charging lamp connection in the three-wire female connector, originally going to the OEM regulator. The instructions for the Enduralast mention rewiring the black starter solenoid wire but it is not necessary in my /5 harness, which stays properly connected without any extra steps. The confusion is over a white two-wire connector coming from the front of the engine, that doesn’t exist in my /5 harness. Overall there is some extra bulkiness to the harness on top of the motor with the Enduralast. I’ll try to clean up the wire loom under the gas tank with tie wraps but you might notice something’s not as slick as stock.

Here’s the new battery I got for the beast, a Panasonic LC-X1220P. $68 delivered from


This is a “maintenance free” 20 Ah AGM-type that fits and some /5 owners recommend. I’m not so averse to checking battery cell electrolyte levels but I recall the vent tube was the source of much corrosion since some sulfuric acid drips out of it. Okay, I’m also spoiled and lazy. Sue me. Curiously, this battery does not come with a protective cover for either battery terminal though it does come with M5 terminal bolts, nuts, and wire-biting washers. I’ll have to rig up some sort of insulator for the positive side.

Here’s my reminder photo that I filled the engine oil pan. This is my last fluid fill. I should be properly wet everywhere except for gas now.


I have to remember to use plain dead-dinosaur oil until the new engine components break in. After that I’m a big fan of the newer synthetics, stuff like Mobil One or Shell Rotella. Heck, since this machine has a dry clutch I don’t have to worry about friction modifiers in the oil like I do for the FJR.

Now I’ve got a special treat for you. Nowhere on the web could I find images of exactly how to route the clutch cable. The service manuals are zero help. I worked through the written descriptions of the clutch cable routing and what follows is a series of photos showing it in detail. It could still be wrong. If so, post a comment. You might think cable routing is trivial but I spent quite a bit of time studying the possibilities and I STILL muffed a couple of them, having to re-do them. I only found my flaws when I got everything routed so it was frustrating.

Okay here’s the start of the clutch cable routing, at the back of the engine. You need to thread the cable from back to front because the back end of the cable will not slip properly coming from the front. The long rubber boot gets hung up and I think the cable flare, trapped in an engine lug, is too large. You can’t miss miss that engine rear engine lug, directly in line with the clutch release arm, so figuring this end out is easy.


Note that getting the clutch cable onto the clutch release lever shown above is the very LAST step in cable routing. I used a cheater-bar to lever it far enough to slip the cable end on. The cable continues between the frame and the engine, under the pushrod tubes. You might imagine you could stuff it in there from above (I did) but you would be wrong. You have to thread it through straight from the rear.


Now it just runs up along the frame front tube. I believe you do not want to tie wrap it anywhere since that would increase cable resistance. Trust me, the new-clutch pull is manly enough without adding any effort.


Now for the possibly controversial part. I ran it through the small upper triangular opening at the steering head. That seemed to give the cable the right amount of slack while not stressing or rubbing it too much when turning.


And it ends at the left hand control.


Voila! I know. Some of you are less impressed than others.

Here are my three-piece stainless steel Keihan header pipes, properly mounted.


They are gorgeous! This picture doesn’t do the stainless finish any justice. The workmanship is superb. I still had a bit of a grunt-fest getting them mounted. It doesn’t take much misalignment to jam up this trilogy of pipes between the two cylinders. I applied anti-seize liberally on the head output port threads and on the inserted stainless surfaces. Probably used too much. I got it all over me. A tiny dab of paste spreads and transfers all over your body and a towel wipe just won’t do it. There are two special washers I didn’t show but the repair manuals are pretty clear on these and their orientation.

I’ve got some Keihan stainless replica exhaust pipes on order from Stan at Rocky Point Cycle (, along with his key-conversion and a Boyer Microdigital ignition) and they should arrive in a couple of weeks. The headers make me feel good about the money I spent on these parts. Stan participates on the Airhead club e-mail list and is well regarded by those guys. Looking back on my purchases, I should have bought my stainless bolt kit from him too. He sells a more thorough kit and tumble-polishes them.

By the way, I got to talking with Stan about the Boyer Microdigital ignition. Turns out it does not interfere with kickstarting as much as some folks led me to believe. The deal is it sparks when it turns itself off, if you don’t turn over the engine within a couple of minutes. There is a built-in timer that shuts down coil energizing after “some” time with the engine not rotating. For unknown-to-me reasons the Boyer ignition fires a spark at that moment (dumping a stored charge?). If you happen to be kick-starting and out-of-phase when it sparks you could get a not-nice kickback. Sounds like a rare event and won’t happen if you start up right after turning the ignition on. Anyway that’s what Stan says. I’ll be another point of anecdotal evidence after I get ‘er installed.

Here is one of the two old fuse holders, which I did not recognize as such before. I just thought they were the funkiest splices I ever saw. Below it is one of the Posi-Lock ATC blade fuse holders I am replacing it with (I happen to have a couple).


Here is the exploded view of that OEM fuse holder.


See that nasty old cylindrical Euro fuse? When I was a college freshman I drove a VW Type III (fastback) beater. It had this type of fuse and they corroded so easily that I got in the habit of rotating them in the fuse box before I would try starting the car! Today that car would be called a hooptie. Of course, hooptie has probably jumped the shark by now.

Here’s the empty headlight shell, whose interior I painted white in a prior post.


Aside from wires, flasher, and fuses it is also missing the keyed ignition. Stan’s kit is due next week and I don’t want to mess with the original (see an earlier post for some pics of it).

Here we are with all the harnesses inserted through their gromets and the speedometer & tachometer cables installed.


These pictures make it look like elves really did come do it for me, eh? Yep, this is when I discovered another incorrect cable routing (speedo has to enter at a relaxed angle) and fixed it.

One quick disappointment was the front turn signal harness was not long enough. Oh maybe it was long enough but I didn’t get the wires routed for max length. I dunno. All I can tell you is several of those wires were short. Here’s me thinking about mounting the ground wire female spade from that harness onto a nearby male spade but encountering shortness.


So close yet so far. I tugged and massaged. Got me an extra quarter inch or so. Grrrr. I made some extension wires (using crimped terminal ends) to make necessary connections. The extension colors are wrong but c’est la guerre.

I also figured out why some of the instrument lights have two posts and some have one. It is all according to the schematic. Three of the lights are jumpered together with a grey-and-black wire. That’s what the second lamp terminals are for. Somewhere on the web I found an on-line owner’s manual and that told me which colored instrument light did what. I think I got ’em all right but we’ll see.

Here’s the work in progress of more busy elves. Er, just one slacker gremlin I guess. I sure had to squint at some of the colors in the schematic and used my ohm-meter liberally to verify where certain wires came from. There’s another green-and-black wire jumper I needed to rig up separate from the harnesses. They tie together at one fuse.


Can’t say I like that black terminal block. The set screws don’t do such a hot job of trapping multi-wire-to-one-screw layout. That is required on at least four of the posts (turn signals). Phew. That was a lot of work. Time for some fun.

Sunday is another episode of Homo Two-Wheelis! In a frying pan! Joe and I rode the Antelope Valley Touring Society’s “Saugus Poker Run.” It sure got hot today. Gary didn’t come along so once again we don’t have an actual temperature reading. On the road, around 7:30 AM, it was really nice. By 10 AM is was hot. Some time around noon it must have touched 100 degrees and we didn’t get home until after 2 PM. We started at Santa Clarita Motorsports.


The run took us over some of the best roads in the area like Soledad Canyon, Bouquet Canyon, and Elizabeth Lake/Lake Hughes roads. This was an true poker run and we drew cards at the start and several stops along the way. The cards were translated into points using a predetermined look-up table not hand values according to Hoyle. I prefer drawing old-fashioned actual hands but this makes it harder to cheat.

Here’s the Half Way House Cafe —


At the start of the ride Joe gave me a gift. A cloth skullcap. You wet it, slap it in the helmet, and it keeps you cool for a while. The only problem is on a 100+ degree ride it dries out in maybe fifteen minutes. I’d show you a picture but it just looks like a blue fabric pancake. I need a water drip system, like a Scott chain oiler, for my head. Anything helps. I used a water-crystal bandanna around my neck and a Chilly Mate personal mister too!

Right after the start of the ride I experienced a communications meltdown. My AutoCom behaved like it had a broken connector wire somewhere. I’ll be messing with it eventually but we rode our ride like stoneage cavemen. I know, that’s an exaggeration but you do get used to the ease of radio communication. Arm flapping just doesn’t help much when you need to discuss whether we just made a wrong turn or not. And there were three poorly-written turn-by-turn instructions today, worse than usual, causing several u-turns and shoulder-shrugs.

Here’s a stop at a park in Towsley Canyon —


And here’s the end, at Saugus Suzuki.


Aside from stopping for cards and a half-hour for a burger at the end we were in the saddle all day. Fun but tiring. When we left I had the high hand with 208 points and only a dozen more people not yet finished. I say my hand stands up. My hand could be described as drawing 41.6 out of an even 1-to-52 distribution, five times in a row. Or about 1-in-3000 odds of doing that well. They’ll mail me the prize if I win. Joe got skunked. Well, we both won door prizes. I got a Race Tech coffee mug and Joe got a plastic bottle. I think I beat him there too.

Here’s our ride pin.


Should just be an image of an oven set to broil.

Let me end this week by asking you if you think I’m the crazy one. No wait, this is about motorcycle clubs and their e-mail lists/bulletin boards. There is a spectrum of how these discussion groups are moderated running from virtually unmoderated to heavy-handed moderation. The Airhead Beemers Club (ABC) is one of the least-moderated e-mail lists I know of. Tangential discussions flourish as long as people want. I don’t mind this too much since topics have subject headings and I can skip over drivel or stuff I’m not interested in. It is a text e-mail so no matter how big the “digests” get it is still a no-time-at-all download over my DSL line. And when there is a technical question the responses are sharp and detailed. So I like that group. and I’m an actual dues-paying (in more than one way) member of the club.

At the other end of the spectrum is 5 United, the /5 owners group. It has no dues so it is just a directed message group, actually a Yahoo group. That group has the most heavy-handed moderation I’ve ever seen. It has been discussed on that board but the organizers don’t want to lighten up. They are afraid it’ll degenerate. But given how the Airheads club functions I don’t understand their fear. Not too many kiddies are interested in /5 BMW’s. Anyway, a fellow on the 5 United group asked a question about the neutral indicator switch on the tranny, what it is supposed to look like from the outside. I just happen to have a perfect photo of that back in this blog so I tried to post a response. Here’s the e-mail chain that resulted between the 5 United moderator and myself. You know how e-mail chains work, read from bottom to top —

From: Kneale Brownson
To: Eric Arnold
Subject: Re: Message not approved: neutral indicator switch

I figure if it’s worth being helpful, it’s worth being fully helpful. If I’m to go to the effort to edit out your URL error, then I figure I might as well get you to supply a link to a page instead of expecting me to hunt for it.

Regards, Kneale

Eric Arnold wrote:
I figure my work to create the blog is enough. Pointing to the page and post is a courtesy. Your rejecting my post makes no sense, given just how specific my help is in this case. You want to let the original poster flounder rather than put this post up and maybe edit out that comma? Makes me question the value of 5 united’s list.


—– Original Message ———-
From: kmbski
To: forhirepen
Subject: Message not approved: neutral indicator switch

Why don’t YOU find it and supply a link to that page?

Additionally, your link as sent doesn’t work. Probably the comma
after the .com

Regards, Kneale

> I’ve got a decent photo of this in my restoration blog, go back six
> pages at, look for the post
> titled “Walk Toward the Light” and you’ll find it.
> Eric

So am I the crazy one? I ended up sending a copy of my original response to the person who posted the question, directly to his e-mail. But to my way of thinking Kneale is way off base, demanding that not only I fix the typo of a comma at my link (no big deal, I agree) but that I should have provided a link to that pinpoint location in my blog or he won’t post my response. I dunno. Rubs me the wrong way, like I’m getting too much of the high hat treatment. How far from reasonable am I here?

See you next week!

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