1966 BMW R69S Restoration: January 2000
2000 January 1 (Saturday)
Happy New Year! Happy New Millennium! It will be a happy whatever for me as the bike will go back together this year. Today it’s time to check if I really tweaked the crank.
The short answer is yes, I tweaked the crank. Or did I… read on.
The rear end is just over 0.001. I believe the spec calls for 0.0008. The front, however, is out by over 0.004. Joe thinks he’ll be able to work on it this week, perhaps on Sunday.
2000 January 8 (Saturday)
Joe straightened the front of the crank, but still had some concerns. I brought in the flywheel and we used his “flywheel check” setup - an older case split in half to hold the crank with bearings that had been honed so they’d just slide over the crank without having to be pressed on. Results: no change, the flywheel runout is still about 0.018 - 0.020.
Checking crank journal
The crank is held in the lathe on centers to check the bearing surface and the cone. The bearing surface is right on… the indicator barely moves between two marks 0.0005 inch apart. The problem is with the cone (which means it’s most likely been that way for a long time). Joe’s going to work on it this week.
2000 January 13 (Thursday)
Joe called and asked me to come over to his shop as he had time to spend on my crank. I didn’t bring my camera, so did not get pictures of a complete crank rebuild. Stupid me.
Joe had determined that the rear web of my crank was bad with the cone and the journal seemingly having different centers. He had a spare crank that had been taken apart due to bad bad rods and bearings. I had new rods in my crank. That’s the making of one good crank.
He pressed my crank apart, fit my rods to his spare crank which required different roller bearings and a very slight honing of the big ends of my rods, pressed the rebuilt crank back together, and then put it on the stand and used some wedges and a big brass hammer to get the crank true. I think the final step was to press the plug into the crank pin and check that nothing had moved. Amazing.