KX Riders

Maintenance & Technical => KX250 / KX125 => Topic started by: cowboyshooter04 on June 16, 2014, 08:51:00 AM

Title: kx125 low power
Post by: cowboyshooter04 on June 16, 2014, 08:51:00 AM

i bought my son a 1998 kx125 a few months ago ,the guy i bought it from said he had just rebuilt it & it had not been broken in yet & told me to ride it easy for few days ,we did it seemed to ride ok ,the first time we rode it hard it ran good for about an hour, it got where it would only run at wide open throttle & was really hard to start , i ran a compression test & found low compression ,i think it was around 96-116 lbs , i found the water pump inner gear loose on the shaft ,the guy new it because the outer propeller bolt was gone & the propeller was just laying in the housing ,i found the piston gaulded & ring broke ,i had the cylinder checked by honed by a local machine shop ,checked the head & was ok , i replaced piston & rings ,bike starts & runs great ,but doesn't seem to have much power as i expected ,it wont pull the front tire in any gear ,not even on pavement unless you really pull on it , the compression is about 125-130 lbs ,never got to ride it enough before  to know how it was running before (can you hone those plated cylinders?) what should the compression be,thanks

Title: Re: kx125 low power
Post by: Foxx4Beaver on June 16, 2014, 08:55:22 AM

have you verified if the KIPS valves are working/opening?

not to rub salt in your wounds...but I JUST posted an ad for a 125 the other day, and made fun of the guys comment..."fresh rebuild, not even broken in yet"....
http://www.kxriders.com/forums/index.php/topic,12968.0.html

gotta steer clear of the majority of those sales...unless the seller is gonna tear it apart to show you...which will usually never happen.
Whenever I buy a used bike, I go into it expecting to drop $1000 right off the top, regardless.
Usually by the time I'm done, I'm about $4K into it...usually :roll:

Title: Re: kx125 low power
Post by: cowboyshooter04 on June 16, 2014, 09:56:52 AM

i will check the valves ,thanks for the info ,any idea on what minimum compression is

Title: Re: kx125 low power
Post by: Foxx4Beaver on June 16, 2014, 10:01:20 AM

Quote from: cowboyshooter04 on June 16, 2014, 09:56:52 AM

any idea on what minimum compression is

the Kawie service manual I have says the useable range is between 109psi-171psi...of course you want to be closer to the latter side of that :wink: