Project BMW
Matt's R100 starts the – hopefully – rapid return to former glory with a shiny frame
Iwould really like this R100 on the road by October. Allowing for the newly-opened world filling up weekends and general middle-aged laziness and apathy in the evenings, this means I need to press on. The plan is for an autumnal ride up to Skye with my friend Mikko on his R100 – optimistic I realise, but one needs a goal, you know.
THE FRAME. OH, THE DAMN FRAME.
I'd checked the wheel alignment before spreading the bike all over the county, so was happy of straightness. It was in good order, too, but the surface rust was too much to put up with, even though I'm going for a sympathetic restoration and not a ‘shiny shit' (as we call overly restored bikes) job. So it had to be rubbed down, which was horrid!
BMWs of this age appear to have stove enamelled frames, with a hard, light green primer coat. The enamel just clogs up your abrasive material, whatever you use, and it's all round tube, so you can't use air or power tools. Well, I did use a wire wheel on the rusty parts, before using an oxalic acid to kill the rust. It took an age until I was happy with the finish, enough to apply a coat of zinc primer with an aerosol.
With a thin coat on, I noticed the side plates that hold the pillion pegs and silencers were slightly cracked at the bottom. No issue, so after grinding to clean metal (with a Dremmel as it was a difficult-to-reach nook) I MIG welded both sides. The zinc primer coat also helped me see where more prep was needed, before I could apply the filler primer.
Filler primer, or high build, is finer than filler but thicker than top coat paint, so it will mask minor marks. Before mixing the primer I worked out how best to hold the frame so I could spray the whole thing – not easy! With the frame precariously balanced on my ‘rig' and a length of plumbing pipe, I gave it several coats and was pleased with the results – hours of prep had paid off.
Next the black base coat needed to go on, but moments after I'd applied it, disaster; the paint started to react. It looked like it was burned, with ‘spider's legs' appearing everywhere – I was gutted. There was nothing to do but wait for it to harden, find out why it happened and rub it all down again.
Speaking to my friend, Nick, at Ashtons Classics bodyshop, I checked the paint, the thinners, the spray gun, the hardener and even tried it again on an old car wing
– it did it again. Eventually I checked my compressor, which I am slack at draining every night, but when I did I noticed oil coming out. I worked out I'd had it for more than 25 years and oil was leaking into the air chamber, which then gets into the paint, causing it to react. Bugger.
Nick kindly allowed me to repaint at his booth and recommended I use 2k black, which doesn't need lacquer, yet is just as hardy. He also advised to put it on thick, to try and get a good coverage. This I did, expecting to have runs, but Nick is a master and it produced a great finish, which neither ran, nor reacted! I did have one issue though, which was not putting enough paint on the bottom of the lower frame rails, as when I tilted the gun upwards, the paint isn't going into the nozzle! A second attempt sorted that.
Final thought is that if you're as impatient as me, you'll forget to prepare the other black parts so you could have done them all at once; like the fairing mounts, top subframe, rear subframe and swing arm.
WHEELIE GOOD
The front wheel was apart and the rim looked straight, so worth cleaning up. There's some ‘life scars' but that just tells the story of this 44-year-old machine. Polishing is not my thing and I tried all I had, with little success. In the end I settled for rubbing down with a fine Scotchbrite pad, then using different mops in a drill, before hand-finishing with polish. It took several evenings and I had a dilemma as to lacquer the rim or not before respoking it. In the end, I did with an aerosol lacquer, to help protect the now shiny rim from when I'm lazy and don't clean them. An engine part you can spray with oil to protect, a wheel isn't such a good idea…
Building a BMW wheel is fairly straightforward, once the wheel has bearings fitted. But BMW wheels have taper bearings, which need preloading and we go through this on page 88. The spokes are straight and all the same length, so it is just a case of working with markers and loosening one area and tightening the opposite until it looks straight. It took me two evenings, but I was happy.
The brake disc bells also got lacquered when I did the rim, again to help them fight corrosion. That means the forks, wheel, discs, bar risers and yokes are ready to fit and it's just the calipers that need servicing – but Neville's nicked my new pistons!
TOP END
Having bead-blasted the barrels I had to make a decision about finish. Originally they were bare alloy, though I think BMW lacquered them. But I like the British look and paint will protect them too, so I've painted them black. They then need popping to friends, BDK engineering, who when not racing their Jawa 350, V4, twostroke, can hone the bores. The heads have also been blasted and cleaned up with a Dremmel and mini wire wheels – horrid things that while they work, they shower you and your clothes with tiny wire bristles that end up stabbing you days afterwards – which I will lacquer after they've had the new valve guides fitted, as the heat needed on the head to squeeze them in is a lot – BMW tolerances are much higher than old British engines! I also took the opportunity to clean the carbon out of the exhaust port so the downpipes fit more easily and while there, I couldn't resist removing lips, poor casting and carbon from the rest of the combustion chamber. Every little helps, as they do say.
AND SO…
Momentum is gaining. The bottom end is almost clean and then needs the crankshaft seals fitted. And it'll be easier to refit the electrics and the alternator before the engine gets fitted. With new engine bolts and a rather sturdier way of holding the bike than the pallets I used to dismantle, the front end should be on soon, followed by the top end. Then it's a case of cleaning up and repairs to the loom, ignition, gearbox, rear… October, you say?