fouling from cold

[kwakaman]

hi guys
my 1996 kx 250 fouls plugs from cold on warm up which i have narrowed down to the air screw and pilot jet. now this machine unknown to me when i aquired it second hand has a '99 barrel on it which i resleeved. main jet is ok but bike runs very rich up to 1/3 throttle. what i want to know if someone can tell me is can i go leaner than a 40 or should i look for something else.
main jet 158
pilot 40
air screw 2 turns out
piston and rings are new
carbon reeds
fmf fatty pipe
thanks please help :)

 

[Morvo]

I've been having a problem with my KX250 1995 model and I have heard a lot about the float height causing this plug fouling fiasco. I have adjusted the heights to what Kawasaki specify in the manual, rejetted the carbs to what FMF reccommend (I have a gnarly front powercore II rear). I haven't had the chance to give her a proper thrashing yet as I just got her back to life again the other day after 3 months! I will come back with results after crimbo more than likely as I will probably be slaughtered over these next few weeks :)

 

[Jaybird]

Could it be that you had fuel in the tank that had sat for awhile just before the plug fouled?
I've always felt that there is a chance of some two stroke oils falling out of suspension when sitting. Especially an oil with castor.
If you have a concentration of oil sitting just above the petcock, it is possible to introduce massive amounts of oil right away.
This may not be remotely the case in your instance, just something to think about.
Shake well before using. :)

 

[Tyler3386]

Cold air(as opposed to hot) will not cause it to foul. Cold air is more dense causing your mixture to be leaner than it would be in warm air so the problem is not the temperature. I'd say your filter is dirty or maybe the gas and oil have separated.

 

[ecy063]

I had a simular problem with my 1994 kx. After reading past threads relating to my cold start problem I tore my engine completely down and replaced the crank seals. The theory is that the gear oil was leaking into the crankcase when the bike sat overnite. My bike now starts second kick . It's a pretty big job and risky if you don't have a lot of good experience with motorcycle engines. Good luck. :ride: