I finally go around to inspecting the top end on my MC21SP and found that I have no mark pistons in the C cylinders. I assume the pistons are standard Honda, they have the markings "IN H KV3" and "HF2" on the underside of the skirt.

I have a caliper for measuring, but it is not likely accurate enough to verify the wear of the cylinder and piston. Both cylinders appeared to be 53.924mm while the pistons were ~53.900. I guess I need some more accurate tools, because I do not expect the bore to be less than 54. Or could it? If it were re-plated it could have a smaller bore than 54.

At least I was able to measure the ring gap and found that 0.45 would pass, so new rings are in order.

It has been running fine like this for the past several thousand km when I purchased the bike used. Any thoughts on the no mark pistons in the c cylinder?


Last edited by doug3 on Sat Apr 11, 2009 9:11 am; edited 1 time in total