For example... Take a Rotax 670. How much bigger is the o.d of the cast sleeve than the cylinder in .001" How are they assembled at the factory? Warm cylinder & cold sleeve?

When we sleeved some 670's we were told it should be 3-4 thou.larger than the ID of the cylinder.

Thanks! I would assume .004" on a 740 big bore sleeve.

when I rebuilt my 1050 mach triple one of the sleaves twisted while honing. upon removal we found that it only had .0015 interfearance fit, not enough! .004 should be fine.

.003 - .0035 on the 740 sleeve. I would suggest heating the cylinder to 500 degrees. It is not necessary to cool or chill the sleeve if the cylinder is hot enough.