97 98 kx 250 compatibility

[rickface]

Recently purchased a 97 kx250.  When i test rode the bike it seemed really sluggish at the top end. therefore i figured it needed a new top end. once i get the bike home and start it in my garage and the motor totally bombs. i run a compression test and its at 35psi. i remove the cylinder and it looks like the piston hit the power valve and pretty much ruined the place that the power valve slides into. so i purchased a used cylinder from a 99 that was only missing the short little gear at the bottom of the cylinder for the power valve. so i sent that cylinder to get sleeved, ported and polished, and bored to the 2nd bore. after sending that cylinder to the machine shop i came across a complete 98 parts bike with a seized crank. i purchased that bike also. i guess my 1st question is will that 99 cylinder fit on my 97 bottom end? also will my rad valve interchange from the 97 to the 99? lastly, what parts from the 98 will fit on my 97? the 98 is in alot better shape but has no title. thank you in advance for your replies and help in this matter. any knowledge and suggestions in this matter would be extremely helpful

[tkeen511]

I don't have all the answers but here is what I do know. 97 to 98 are almost identical, pretty much everything you have that fits one will fit the other. The 99 cylinder will bolt on to your bottom end, and should work, but they are not the same. The stock porting of the 97/98 cylinder is a little more towards the low end side, that plus the low first gear made the k models (94-98) a monster in the woods and corners. As far as the power valve, I have no idea. I just know the 99 fits, but I've never heard of anybody actually running one.

[rickface]

thanks for the help. any info is good info. the only reason that i went ahead an had the motor work done to the 99 cylinder instead of the 97 was the owner of the machine shop called to give me the price quote i asked him if he noticed any differences and he said they were the identical cylinder

[rickface]

well you officially know someone that is currently riding a 97 kx250 with a 99 kx250 head. its been sleeved, the power valve cut down, ported and polished, and the head milled down. she is a beast and the power is unbelievable. thmx for all the replys and help everyone

[swordcombat]

Yes your RAD clave will fit and yes the cylinder will fit
And I'm almost certain the power valves are the same also
As I have a 1998 cylinder on my 1999 bottom end