Restoring a 1973 BMW R75/5 Motorcycle

December 28, 2006

Origin

Filed under: 1973, airhead, BMW, motorcycle, R75/5, restore — Penforhire @ 9:22 pm

Hello visitor to my blog.  I’ve never done a blog before and a topic came up that I figured was appropriate to attempt.  A little research on blog sites and, voila(!), WordPress is the one for me.  Bear with me if my blog is clumsy since I am just a newbie or FNG at this.

My father, James Arnold, passed away December 11th, 2006 at age 69, just a few weeks ago, at the Veteran’s Administration hospital in Palo Alto CA.  He had AML (acute myeloid leukemia) so we knew this was coming.  I am 44 years old so my lifespan weighs on my mind as well.  I am significantly overweight and sedentary though I am not a lifetime Camel smoker like my dad.  My dad was not wealthy in material terms and he had no will.  Denial is a powerful emotion.  It cost me more to bury him than the total value of his estate, which I gave the bulk of to my baby half-brother (11 years old, another story eh?).

One of the items dad left behind was a 1973 BMW R75/5 SWB (short wheel base) motorcycle in rough condition.  It was not ridden in years, stored outside, and was never in top shape to start with.  Even though my father stopped riding it he never stopped thinking of himself as a motorcyclist.  He caught the m/c bug in his youth and never let go.  As it happens, this is the very same motorcycle that I learned to ride on about twenty-five years ago!

Dad used to gripe that BMW’s changed for the worse since his older R69 and he regretted selling that one.  I have back-seat memories, riding behind him around the age of ten, but this R75/5 is the symbol from my adult life.

whole-bike-973.jpg

I figure to restore this motorcycle to working condition and keep it as a remembrance of my dad.  If I have any energy and money left I might consider converting it into a sidecar a.k.a hack.  Since I have below-average patience and below-average mechanical ability (for anyone who would hold a wrench to start with) this will make for a lengthy and storied process.  My father and I did not always see eye-to-eye but motorcycling was one medium of our communication.

So what do I remember about this bike?  Well, I always liked its torquey engine.  When revved at a stop the internal motions make this bike tilt.  It had a clutch engagement measured in milli-degrees, abruptly on or off.  Something similar could be said for the drum brakes.  I called them “digital,” they were either on or off with very wooden feel.  Handling was always funky since it was a short wheelbase model and not perfectly maintained.  I remember riding home one day after the throttle cable snapped at the grip, using a pair of pliers to pull on the cable and juggling the controls.  Parts were always more expensive than for other machines but my dad had a sort of mystical confidence in BMW “airheads.”

That is the slang term for BMW boxer-engine (two 180-degree opposed cylinders) motorcycles of this vintage.  There were several series of airheads and their generation is indicated by the number after the slash.  So this one is a /5 (or slash-five).  Before this there were pre-war R-models, then /2’s, and after the /5 there were /6’s and /7’s.  In 1993 design changes made the newer engines “oilheads.”  Around 1984 BMW also came out with what they called the K-series motorcycle, using an in-line engine (3 or 4 cylinder), but those are not the subject of my quest.

One curiousity about the /5 series is the swingarm was lengthened in mid-year 1973 to make a more stable touring-type bike.  So when anyone talks about a R75/5 they have to also specify early short wheelbase (SWB) or later long wheelbase (LWB).  A properly maintained SWB is supposed to be a bit livelier but an improperly maintained SWB feels like a deathtrap, wobbling and pogoing in corners.  Sitting on it now, after riding my 2005 Yamaha FJR1300ABS, I am struck by how small the bike feels and how you sit on top of it, not as much “in” it as modern high-rise gas tanks make you feel. 

 I fell over at the very first u-turn I ever made on this R75/5, at the end of a cul-de-sac in Redwood City CA where we lived.  I was so upset because I broke the side mirror and I knew my dad would be angry.  Nope.  He bust a gut laughing.  Over the years, whenever we talked about that moment I’d turn red and he’d laugh.  Dropping a bike at any speed is always embarassing to me because there is a lack of control implied.  Exercising control is one of the benefits I get from motorcycling.  Dad was more a student of Robert Pirsig’s “Zen and the Art of Motorcycle Maintenance.”  Everything about a bike was a metaphor for something else in life or some life-lesson.

So anyway, I had the motorcycle shipped to me since I live near Los Angeles and it was not in rideable shape.  I ordered the Clymer and Haynes repair manuals.  I scoured the web, finding sites like “5 United” and Airheads.org.  I cleared a space in the garage and I bought a couple of necessities for dealing with old stubborn mechanisms like a manual impact wrench.  You know I like anything powered by a hammer!  If you’ve read around on the topic of airhead restoration you may have come across the “Carb Chronicles” and that sort of inspired this blog.  I’m a bit like the fellow who wrote that one, clumsy with a wrench but determined to try.  So spill a few pints to the airhead gods for me too!

I have one secret weapon in my arsenal.  My regular riding buddy Joe is a cracker-jack whiz-bang airhead mechanic.  While he sold his similar-vintage airhead a few years back (and now rides a hot-rodded K1200RS) he kept all his specialty tools and a truckload of parts.  He said something about having a spare centerstand and that sure would be handy, since the foot-tang rusted off mine!  I saw his old airhead stripped down to a bare frame, reassembled, and running again.  He did it all, excepting stuff like valve grinding, himself.  The man has no fear!  He still has a shim-plate he made for reassembling his transmission properly.  Me, I get sweats thinking about gummed up Bing carbs.  I’d never have the guts to ever see my tranny gears and assume that machine will ever function again.  Those are parts that go where the sun doesn’t shine.  Enter at your own risk!  Or maybe it’s brains not guts, for just knowing it would not function again?  This could take a while and involve lots of crying and professional help…

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