Originally Posted by bboy
New bee question ... help.
I just got a new OS TZ12 5 port and before breaking in, I notice when I turn the crankshaft, the cylinder liner is hitting against the head/heatsink.
Is this normal? I was rotating the crankshaft and it seems to be stuck every 180 degree, then I told off the head to find out that the piston is pushing up the liner above the square position and hitting the head.
Just put everything back to original condition.
The piston is not hitting the top ( underhead ).
It's the pinch that creates the feeling of stuckness.
Smear some after run oil at the pinch area. Two drops of oil in conrod / crankshaft. Three drops in rear bearing, and you can start the break in process.
I believe OS also give you 1 more shim in the box, use that for break in process. Additional shim helps to reduce the work load for conrod, get more stable idle, and reduce engine compression.
OS engines usually takes very long time to break in. Even after 1 race, sometimes the pinch stuckness is still there. Don't worry.... it's good thing.