Boxerworks.com

Finally finished the rebuild on the 75 R90 S and have her all back together. Was wondering if there would be a break in period since I did put new rings in ? I took her to the gas station and filled up then took the long way back home. She rode and sounded beautiful. No smoking from either cylinder. Guess I got everything back together correctly.

EDIT: I want to thanks dwerbil and Kurt in SA for giving me the courage to undertake this job, especially with the rings. THANKS guys

Nice going!

IMO break-in should include sustained riding, limited idling, and running up and down on the revs to increasing the forces to push the rings against the cylinder walls. I'd keep it to maybe 75% max RPM in each gear. I'd also change oil somewhat frequently and check valve clearances at regular intervals. The last two bikes I broke in I dropped the oil after the first 20-30 mile ride...it will have a fair amount of ring material in it...this might have been more important on my R69S with no oil filter. I wouldn't use a full synthetic during break-in...it allows too much sliding and not as much wearing in of the rings.

Tom Cutter suggests that the initial start and run-in does a lot of the break-in. Once the oil gets splashed up onto the lower ends of the cylinder walls and the heat glazes the walls, break-in begins to slow down. This site might be a bit extreme but has some thoughts on the break-in procedure.

http://www.mototuneusa.com/break_in_secrets.htm

Kurt in S.A.