Posts
14
Joined
6/19/2022
Location
CA
the bike has around 35 hours and im trying to do a top end and ive called the place that sells it "royal distributing" and they said that ill be fine having it as it's the standard size. Also on the website there was no option of A,B,C, or D and it came in the other day showing it with a size 53.95, what do you guys think?
Might be totally fine too, but on a 125 especially would
Scare me but I’m super anal about that stuff lol.
Usually you do A cylinder with A piston then go to B piston. Then replate. So in your case C cylinder with C piston then goto D piston then replate.
I think, it's been a while for 2strokes for me.
The Shop
You are going to have to measure or just take the risk.
7. Before installation, the size of each individual piston should always be checked. In
general pistons should be measured on a 90 degrees angle to the wrist pin and
at 25% of the piston length from the bottom of the skirt. The piston and cylinder
size should result in correct piston to cylinder wall clearance for the specific
model. The chart below gives a general indication of clearance by capacity but
original model specifications should always supersede the table below.
Recommended maximum hours use. (competition) / normal.
0,05mm0,06mm
or
0.0020”-
0.0025”
Although the included piston rings are matched for the specific piston and bore
size, the rings on the piston should always be checked on the ring end gap
specifications. The ring gap should be around 0.4 to 0.5% of the piston diameter
and can be measured by placing the ring in the cylinder and using a feeler
cauge. Normally it is not needed to modify the ring gap.
9. It is not needed to check or modify the ring gap on oil control rings. The ring gap
on the second ring should always be larger than the gap in the top compression
ring.
I have a brand new stock piston for my YZ250 that was the wrong lettering. I could have used it.....it probably would have been no problem but these bikes are my babies.
Answer: Wiseco Powersports pistons are designed for optimal piston to wall clearance for the specific bore size of your engine. For example, your 125cc dirt bike engine is 54mm bore, the Wiseco piston is designed just for that bore size, and does not require any specific adjustments to fit properly.
Here's quote I lifted from another forum:
'A' = 53.957 - 53.960
'B' = 53.961 - 53.964
'C' = 53.965 - 53.968
'D' = 53.969 - 53.972
It's sometimes been said, grasp an A piston in your hand for a few minutes
and your body heat alone will make it expand almost into the B size tolerances.
That said, I'd probably advise against running a smaller piston in a larger bore. Get the right size or one size larger.
The pistons which are "one size fits all" are likely equivalent to "D" pistons.
Post a reply to: should i run an "A" size Pro X piston in my "C" size cylinder on my 2017 yz125