Hey, I’ve got myself a 1982 BMW R100 I’ve spent the last 2 months trying to get back on the road. I’ve surpassed all feats, including but not limited to; Wheel bearings, steering head bearings, tire replacement, pad replacement, all oils swapped, forks rebuilt (all of which done successfully), and master cylinder (almost done successfully)
My question regards the bore of the cylinder. When I got the bike, the remaining fluid has begun to crystallize whilst sitting in an a/c controlled garage for the last 23 years. I noticed some nasty crud built up around the ports here and there, and some down the bore of the cylinder, but it didn’t seem to be any match for some brake cleaner. I installed a new master cylinder kit with care, and I was home free. 3 weeks passed and now I see I’m leaking quite heavily between the face of the M/C and the throttle perch, though only from use of the front brake, not just sitting. Pulled the cylinder this morning, and noticed it squirted out past the inner seal (near the head of the piston, not the one in the throttle perch). Because it was a new Magura, I’m convinced it must be the bore it’s self causing issues.
Now I’ve had a rigorous shakedown test on the bike planned for next weekend, but I don’t wish to get brake fluid on my tank. Would a viable attempt be to pull the cylinder, and try to clean the cylinder more aggressively, be that with a brass brush or plastic brush with a lot of brake cleaner and hope it works? I hadn’t noticed any actual pitting in the bore, just general aluminum oxidation, but perhaps vinegar could help brake that edge and bring the rubber piston ring closer to the bore?
Thanks for any advice, I’m new to air heads so bear with my on terminology!