Maintenance & Technical > KX250 / KX125

She's Alive !

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TaKeN:
Ok, its still not running right and i can't figure out why.


It has plenty of compression because it blows your finger off the plug hole every time you push the kickstart down.


It pulls well when its beggining to warm up, but once the engine gets quite hot the bike starts missfiring and the power isn't clean...   :|

I'm realy confused as to whats wrong with the bike, i stripped the top end down tonight after it got hot and the bore looked fine.

There was no unburn't oil ontop of the piston...


Ive also just gone from 33.1 to 40.1... using Castrol TTS.


Is the jetting out by miles ?

could it be the timing ?


Please help my guys, i'm getting realy annoyed with this bike and its starting to make me want to go and buy something more reliable like a Honda CR Motocross bike  :-o

There was also alot of smoke coming out of the back of the bike at one point and it didn't smell like two stroke oil being burn't :|

Maybe the crankcase is sucking in tranny oil ? ( Although this isn't running low )

BigGreenMachine:
I do my break in different and the correct way IMO.

Start the bike, make sure there are no leaks and everything is fine. Ride it around a little to warm it up. Once its warm ride it like you normally would making sure to go through all the rev ranges. Make sure to keep the clutch out after downshifting to keep load on the engine. After about a 20 minute ride it will be broken in.

After the ride let the bike cool completely then retorque all the head/cylinder nuts back to spec.

MadKaw:
you changed your oil mix, that also changes the jetting needs. have you repacked your muffler packing recently? how did your plug look when you torr it back down? probably jetting.

and don't fool yourself, all brands have to be tuned right.

alan:
I am not sure about some of the other problems you are having, but "It has plenty of compression because it blows your finger off the plug hole every time you push the kick start down." Is not an acceptable means of checking your compression!

don46:
I would agree with Alan that using your finger is not a adequate means of checking compression. You just rebuilt it so I wouldn't think compression would be an issue. The procedure used to break in your bike will ultimately determine the longevity of you piston, the main thing is to make sure your bike is warm before you get on it to prevent a cold seizure and that holds true even with a well used bike. Lets face it the factory boys don't go out and breakin their bikes before a race, but they do get freshened up before every race.It sounds to me like jetting, it runs fine till it gets hot then loses it on top end. I don't remember what year it is, does it have a power jet? I recently found a problem where the powerjet failed, the bike ran fine up to about 5/8 throttle, after that it would act like it was flooded out, close the throttle and it ran fine. I wasn't using the power jet circuit on the carb so I just plugged it, you may need it on your bike, as I recall there is an RPM range it cuts in and then cuts out.

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