Need help

[peltonr]

I have a 97 CR250, After having the bike two days the pistion ring did a number on the cylinder wall. I bought a top end off the net with piston from a 96 CR250. I now have a surge when the bike is worm but runs vary well when cold. I have changed all of the gaskets twice from crank to top end. Had carb rejetted but have the same problems. I finaly took the bike to a Honda dealer and they tore the top end down and told me that it was the wrong year piston causing the problem. I knew the piston was a 96 already but was told by this would be no problem from the person I bought the top end from. Could any one tell me if this is my problem.

[dogger315]

It's a common misconception that all '92-'01 CR250 engine parts are
interchangeable - they're not.

The breaks are '92-'96, '97-'98, '99, '00-'01 and '02-'07.

The '97 piston is not compatible with a '96 cylinder and head
and vice versa. If you have a '96 cylinder AND head, you have
to use a '92-'96 piston. The port timing will be different than
what your '97's ignition map and power jet carburetor is set up
for so you will probably have a strange power curve. The head
shape is the biggest problem, being designed for a flat top vs.
domed piston.

'97 was a strange year for Honda and the CR250. In '99 they
dumped the troublesome power jet carb and totally changed the
map and port timing and the motor finally started producing some
serious useable power again by '00.

I recommend you clean up the '96 top end and sell it on Ebay then
buy a used '97 top end. It's the only one totally compatible with the
rest of your set-up.

dogger

[Woody_393]

Great info Dogger

[mxman107]

any why to tell year with the cylinder

[peltonr]

Thanks for the info.

[dogger315]

any why to tell year with the cylinder

Good question. On the right side of the reed valve casting, Honda
stamps a code. "KZ3" Honda speak for a CR250 and below will be a
letter. My '93 has a "J", my '96 has an "N". I have never found a
source for these codes but I have always been able to call my local
Honda dealer, give him the letter and he tells me what year.

Starting in '97 you will also have to deal with the "A" and "B" cylinders
and pistons.

dogger

[mxman107]

kz3-v is a 01 cylinder just to let everyone know.