Breaking in a 2 stroke

Important to remember, most (All?) GP bikes were nikasil liners... Most kart bores are iron. The 125cc shifters being the most common exception. Its all well and good to look at GP bikes but you have to pick and choose what you are comparing it doesn't all translate over to karts.
 
Pete, did you ever see the Honda GP engine years ago with the oval pistons & 2 rods/piston? Bet that one was a hoot to fit a piston.. :)
 
During my years racing FIA/CIK in Europe ICA engines used to have very narrow tolerances and ran very high rpms on direct drive configuration, so breaking in engines properly was a must. Every builder would recommend to do so. We used to make 3 different 10 minute runs at the track, letting engine cool completely between then and increasing rpms till reaching top by the end of 3rd run. We were advided not to run top rpms in the straights but try to keep them accelerate slow through turns. I usually used same oil (Shell racing M) but ran it richer both in oil percentage and carburation setup. It always worked good and if we didn't follow the process properly we used to have issues. That was my experience with those engines. Obviously I can't do this nowadays on my dirt oval open engines.
 
vintagequest: Yes... I was at Laguna Seca when Freddy Spencer won a heat race on it... the *only* race it ever won, to the best of my knowledge.

I managed to sneak a couple of photos of an extra engine in the back of the truck. :)
 
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