I think it boils down to "how round does it have to be." The bottom line is that no circle is PERFECTLY round anyways... we can get pretty darn close with specialty jig grinders and such, but never absolutely perfect. Ihave actually measured the total runout of the pinch area of one of these sleeves before and after repinch... it doesn't change but a tenth or two (.0001 - .0002). Hardly enough to cause an issue. If the piston were spinning around in a circle as it goes up and down then I would say roundness of the bore would matter, but that's not how it works. The piston wears into the shape of the bore, regardless of whether it's a couple tenths out of round or not. It could almost be an oval shape and still work.

I suppose you could have the inside of the sleeve chrome plated and then set up and jig grind a precision taper inside of the bore... you would get a hole that's probably more round than the pistons come stock... but I really don't think there would be any benefit, and it would cost alot more money and take alot more time. Pinching sure seems to be an economical way to get performance back.

As a side note, I picked up a used os .18tm for the revo... I bought it soley for the carb cause it's a direct fit into the 3.3, but I think the existing engine parts are actually rebuildable. New bushings in the back plate and conrod, a re-pinch, and I think I will be good to go. Now, the repinch on this one is going to be a bit different than what Ihave done thus far.... someone beat the tar out of this thing, and the piston almost goes all the way through. Looks like they loaded the fuel up with tons of castor oil to get compression up and keep it running... it was clearly running HOT.. and it was a real bear to get the inside clean. Maybe there is too much wear on the piston, I don't know... I'll pinch it and see what happens.

Cheers