97 kx 125 power loss

vicjac · Apr 20, 2010

Hello, guys. Have a 97 kx125 and just did new ring & piston, seal o-rings, cleaned up powervalves, and other parts.
I just took bike out to break it in and it lugs out really bad @ take off or if i hit the throttle (bike has allready been gently broken in). When its in the powerband it screams but up hill or out of a turn its gutless. I have to have the clutch in and get it in the powerband to get it to move. Been messing w/ carb and cant get it right.
Please Help :bang:

mathd · Apr 20, 2010

I would check the compression and carburator and spark plug.
The powervalve is not gummed open ?

vicjac · Apr 20, 2010

will check it.

rmc_olderthandirt · Apr 20, 2010

Give us some history: How was the bike before you rebuilt the top end?

If it ran fine before the rebuild then I would look for something put together incorrectly. My first guess would be an air leak that is causing the mixture to lean out.

Like Mathd said, if the power valve was not hooked up or is jammed some how then it could cause similar problems. If you can remove a cover over the linkage to the power valve then you should be able to watch it operate as you rev up the engine.

If you don't know the history (as in you bought it in need of the rebuild) then I would recommend starting with the carburetor jetting exercise.

Rod

vicjac · Apr 22, 2010

thanks, the engine was bought used, cus i had a bad crank bearing, cyl, piston, ring. Used motor has good bottom end and cyl. Cleaned the powervalves (felt siezed) and now nice and smooth. When I took the powervalve cover off and reved it the powervalves mech didn't move (1st time messing w/ powervalves). I can pull them, so they r free. Bike is great in the powerband but lugs @ the bottom. Thanks.

rmc_olderthandirt · Apr 22, 2010

I would say that there is something wrong in the power valve linkage or the governor. I know from personal experience that it is easy to get the governor assembled incorrectly...

Rod

vicjac · Apr 22, 2010

Thanks, I'll look @ the manual and hopefully get it right. The reeds were in good shape, so I'll try to powervalve assembly. Thanks Again,

vicjac · Apr 25, 2010

the governer was missing a bolt to where it hang on to the lever. Put a new bolt and still no difference. My air filter is old but still looks good (not torn) could it be this? Should I take to a shop and do a leak down test?

mathd · Apr 25, 2010

Humm ok.
What the spark plug is telling you?
Make sure the air filter is clean and fresh oiled, make sure the carburator is clean and set to the latest working setting(if you ever made jetting change). How is the silencer packing(this one do not really matter but who know)?
Have you did a compression test?

To me it sound like the plug get fouled at low rpm, you sure that reeds is sealing right, and pilot circuit is not messed? no chipped corner on reeds etc. Or maby compression is too low.

Or maby it is the spark plug circuit. Make sure the coil/cdi are ground correctly(on rebuild maby a ground was left with poor contact) or if you have the manual i would check the cdi/coil/stator with a multimeter.

I would check that before a leak down test.
If all this fail and no one else in the forum have a glue then i say go to the shop :(.

Matt90GT · Apr 25, 2010

if you do not know what you are doing with the power valves, good chance you have them mistimed. Take the bike to someone before you do damage to it or buy a manual

vicjac · Apr 26, 2010

I hope not I have the manual. I matched the timing marks to wut it said in the manual. I took the pipe off and they are opening up even. If the timing was off the valves wouldn't open or would they? I have it @ buddy's shop right now, hopefully he can get it right.

CLUTCH444 · Apr 26, 2010

You said you were having problems at the bottom end. This could be due to a wrong pilot jet. You had said that you cant get the carb right, id set the idle and air fuel mixture to stock, start the bike, adjust the idle while its on the stand, then take it out, if it feels weak on the bottom end, richen it up, all this time checking your spark.

vicjac · Apr 26, 2010

thanks i'll try that, I'm hoping its carb work instead of something more expensive.

vicjac · Apr 30, 2010

Got it, I had a bad crank seal on the stator side. I didn't bother to check this side since I did the complete other side, luckily I had an extra crank seal. Bike rides great now, thanks guys appreciate all the help.

97 kx 125 power loss

Similar Topics

Privacy & Transparency

Privacy & Transparency