Restoring a 1973 BMW R75/5 Motorcycle

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!



  1. Re: 5 United comments.
    You didn’t tell me about
    this butthole yesterday.
    He is not only off base, he’s out of the base line. I guess the only
    thing I would say to this guy is Gee thanks for all your help. And follow with two words, and they are not, “Love You!”
    What a jerk!
    Did the guy get your e-mail?
    BMW Joe

    Comment by BMW Joe — August 13, 2007 @ 12:57 pm

  2. You should _definitely_ try to find a jar of BLUE MAGIC polishing compound. It is the best alloy/chrome polishing stuff I have ever tried(and requires FAR less elbow grease).
    I think I got mine at Kragen.

    Good luck!

    r75 looks great!

    Comment by el_knobero — August 17, 2007 @ 3:51 pm

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