Do A,B,C spec pistons really matter?

[GMP]

I do the same thing, good plan. Also, there is a scotchbrite hone available from Mcmaster, that works great in a 250/300 cyl.

[stay_upright]

Originally Posted by hannesd

don't just guess what size of piston you're about to use!
measure with a 3-point caliper as stay-upright says!
only then can you determine what size of piston the cilinder needs...
i allso wouldn't go back a size from B to A, the scoring may have been from lack of lubrication one time or over heating.
stick with the same size or hone the sleeve lightly out and fit the larger size if needed.

hannes.

That's what I did the previous owner had put a B in it assuming the cylinder would have worn but I put an A in it as that was correct for the size of the cylinder. In fact even with an A piston I was still slightly shy of the clearance recommended by GG - but that's how they made the cylinder. I'm happier having the correct piston, it's simply going to reduce the chances of cold seizure, partial seizure and/or picking up on the piston/walls.

My advice would be put the piston in, as marked on the barrel in the bike unless you have accurate measurements to back up the fact you need a larger piston. The cylinders simply don't seem to wear. and IMO every one-else is simply guessing and cold or partial seizures seem to happen quite a lot.

[desertgasser300]

I cannot find a stamp on mine anywhere on the cylinder. Was it different for 97's

[jostby]

I think they were made by TM at that time(?).

[tm_enduro]

Originally Posted by jostby

I think they were made by TM at that time(?).

TM engines are marked too, although my '98 TM was market with ink. BTW, the '97 GG was a GG motor, not TM.