John’s advice... from earth cables to forks
Choosing a BMW R100 was a purely selfish decision. I had always wanted one and an example turned up which, because it needed restoration, was in my price range.
The interest from readers has been nothing short of incredible. I have had, and still receive, dozens of emails and letters from present and previous BMW boxer owners. They praise the bike, they show their happiness about reading BMW-related features, and they offer advice. I have even had parts I need sent to me (thanks Paul Smith!). It’s great to feel that we’re on the right track with the bikes we feature – for some of you at least, but it also helps with the momentum of the project. So thank you.
Here’s one of the best letters, from John Marshall. Enjoy what has taken him years to learn!
Dear Matt,
Things move slowly down ‘ere in Devon. Actually, I am from Wiltshire. More accurately, I am from Wendover, but there you go. I have just got to read about the R100RS resto you have undertaken. I am no kind of engineer and can still remember sitting in the road outside my mum’s in Wroughton fixing my C15 using red Hermetite and roadside gravel. Anyhow, I had a 1979 R100RS which cost £900 relatively recently and took me to MotoGP at Le Mans (Camping Rouge, bit like Bartertown), Belgium, Dijon and Dent to name but some.
My top tips are as follows:
■ Twin ATE caliper brakes basically not as good as the bike’s performance. In the rebuild kit for master cylinder piston, one seal is a sod. To get it on so, go to B&Q, steal a mastic gun nozzle, cut to approx correct diameter, spit on it and slide the seal up and on.
■ My calipers were a bluish silver I sprayed with a rattle can in a similar colour, which worked fine.
■ Under the m/c is the starter relay. It will not be happy getting brake fluid on it. All the electrics go through this as well in some weird German way. Remove and clean, or get a new one. Cover with bit of plastic sheet or similar so brake fluid cannot get to it.
■ Earth cable. This bolts to rear of gearbox in a supremely rubbish design, held by only about 6mm of thread. When replacing the speedo cable, the black plastic fitment usually turns on the cable or the metal ferrule end is not properly located, then when you retighten that bolt it strips. I would suggest an insert like Unithread.
■ If the earth cable is not properly clean and fitted tightly you will get a ‘clicky’ solenoid. Wheel bearings. Another sod. The wedding band spacer!
■ You may try the “shake the wheel test” when retorquing the spindle. Or read all the stuff from Snowbums website, if you can stand it (bmwmotorcycletech.info).
■ Bottom of forks: Nut retaining bottom leg screws onto Allen headed retaining bolt in bottom of damper rod. You can round off the Allen or snap it when tightening.
■ In the bottom of the fork leg is a piece of Parmesan cheese that once was a bump stop. To undo the large bottom nut, best to clamp nut in a vice, then turn the fork leg with a bar. Only use thin oil of the revised amount; it is wrong in the books, I think about 5w is okay.
■ Steering head bearings get dry. You can get the races out from the headstock using blobs of weld but I got a puller set from Cyleworks as no welding gear.
■ Clutch: The RS can get through a clutch much quicker than the lesser powered bikes. Pilot jets clog. You will lose a cylinder at low throttle, then get full power at bigger throttle, nice in traffic!
■ Top carb screws can seize. You better not have a rear disc. I did. A sod again.
■ Headlamp: That front glass can break if a stone hits. I had a spare so no worries. My wiring inside the headlamp looked like new though. Clock and voltmeter a godsend.
■ You can tell the brake light is okay by watching the meter dip. If the meter damping is shot, the needle will swing a lot when indicating but it does not matter.
■ Tank: Can rust on left due to being on side stand. I used POR15 motorcycle repair kit. Used on 3x BMW, 2x Morini and two old lawnmowers.
■ Coils: Make sure wire joining them (white lead?) has firm spade ends. Make sure earths are clean. Whenever tank is off.
■ NGK plug caps work best. Fit a new clutch cable. Clean and lube speedo inner to prevent seizing.
■ Be very careful working on instruments. Make sure rear plug is located and pins are clean. Peripheral screws go into brass inserts within the housing but these seize, the plastic cracks and the brass inserts come out. Bit of patience and Qbond, or can even get new if you’re flush. Make sure any Cyanoacrylate is dry or it can fog instruments.
■ Circuit board within. Getting knackered. Katdash sounds good, though I cannot afford one.
■ Gearbox: A “consumable item”. Best to learn how to rebuild one. Need a puller for output flange and an end plate of known thickness to do shimming. For information I use Jorgs Gearbox (schweizerschrauber.ch) including spreadsheet, and Brook Reams is good too (brook.reams.me).
■ Stands: BSOB time. Centre stand, never tread on tang to put on stand, put boot on stand itself for final grunt. Check pivot bolts, make sure they’re lubed and always tight. Frame threads will strip. Stand may over rotate due to wear, new bushes are useful too.
■ Side stand pivot pin and frame can wear, causing prodigious lean. Stand should retract and likely flip into clip if present with mounts on engine stud with exhaust clamp area.
■ Engine studs. Good to give these a bit of grease or they will seize in situ.
■ Battery: I fit Xtreme600 as you can get them out without removing all the air filter nonsense.
■ The starter needs all the amps it can get in winter. That’s another job; clean and it and rebuild. Getting the left hand starter bolt out. Small hole in casting allows narrow socket extension through.
■ Toolkit I put the roll in a suitable clear bag to keep dry.
■ Get an Oxford flexible tyre inflator tube and keep under seat. Much better than those crappy metal right-angled ones.
■ My snowflake wheels were black with muck. I totally degreased with abrasive scouring pads and a lot of gunk/brake cleaner/washing-up liquid. Carefully masked tyre beads and central hub, having removed discs. Sprayed and lacquered with Simoniz wheel silver. Three years later, bloody brilliant – did not even remove tyres. What a bodge.
■ Exhaust rose nuts: Remove with proper tool, use proper Optimol TA paste, not Copperslip. If stuck can cut with Dremel. Nightmare.
■ Driveshaft filler plug at rear by shock mount can strip for fun.
■ I use copper washers for plugs, some use ally ones.
■ With all that you wonder how there is time to ride the thing. I sold mine after coming back from the Airhead meeting in Lincs a few years ago. Reason was I was blasting down the Fosse Way and overtook a big Jap Cruiser that was not going slow and, after an hour, stopped for fuel and a Mars Bar. The cruiser didn’t come by until I had finished the Mars
Bar. At that point I knew riding at 85mph was going to get me done or worse.
Hope this all helps,
John Marshall in Sunny Exeter