looking for new parts....confused

[ftw2012]

hey im just trying to get a new piston, cylinder (or sleeve) and top end kit for my 03 cr250r and i am getting a little confused on whether i have cylinder A or cylinder B and if i need piston A or piston B....i need both piston and cylinder so does that mean i can just buy cylinder B and piston B and then id be ok or does it have to be the same in order to bolt in correctly? dont know if i explained it very well but thanks for any help!

P.S. anyone have any suggestions on which brands will be work the best for someone who doesnt need to go the fastest or jump the farthest im just learning and will mainly be doing light trail riding ...? thanks again

 

[jrf4x4]

They mean different sizes in id and od , and why do you need the new cylinder

 

[ftw2012]

well i say i need a new cylinder because when i look down the cylinder i have there is a crack going between the 2 exhaust ports.....thats why i think i might just be able to get a new sleeve ...i was just thinking a new cylinder because then i would know for sure that everything was fine.....i do know for sure that i would need to have the cylinder replated anyway because of some scoring...i guess im just new and guessing about what i should do...

 

[Matt90GT]

If you are getting a new cylinder from Honda, then you run the A piston. Best bet is to get the cylinder, measure the bore and then order the piston. B piston is the next wear at .01" greater

If you are going to send it off to get sleeved, then buy a piston A or aftermarket like a wiseco and send it with the cylinder. You most likely have the option of buying a piston from the people doing the sleeve of the cylinder also. But they have to be matched up for the correct tolerances - which the shop will do for you.

 

[mathd]

This is confusing me too. I already rebuild 4 stroke but not 2.
I plan to get a wiseco top end kit without change my cylinder(been changed a year ago by previous owner).
But the A B C size, what to buy confuse me.
Also, do 2 stroke need oversize rings?.. if it even exist.

 

[Matt90GT]

You have to MEASURE THE BORE. It is that simple. Once you know the bore measurement, you can get the correct piston. There is no other way to do it.