Dave, sorry not to get back to you sooner. Interesting question. Should be aiming for .001 clearance on the drive,crank and pinion, thats effectively 0.0005"each roller , eg 1.000 inch crank pin , 2x 0.250 rolls, 0.001 clearance = a big end honed to 1.501 . However , any run out on the pinion and drive will make these clearances create tight spots. It also helps to be aware that housings may not be uniform ( I usually hone new pinion housings before putting them in ) . Also new pins may be (and often are ) a few tenths of a thou oversize, so you need to measure and adjust accordingly..0015 would not be a problem on the mains, some people go a touch more than this, probably to compensate for misaligned flywheels. Racers often run 0.002 -0.0025 clearance on the crankpin, again , thats loose to me , but not destructive. I asked One old sport scout builder what he used for clearances , and he said depends whose running them in !! He would aim for 0.001 on the big end for a road bike if he was running it in, .0015 if it was someone else, and .002 if he thought the bloke was an idiot, and would go full bore from the first ride.
Jorgen Sundberg in Sweden , a top motor builder, recommends 1500 miles as a decent running in period.
Stock clearance for shaft in bronze bushings in timing case 0.0015 "
Hope this helps.
Tim
