2-stroke ktm carb problems

[YamaB]

So I've been having some problems with my '08 300xcw fouling plugs. I went ahead and took the carb out this weekend, put in a leaner (165 to 162) main jet and moved the clip on the needle up one position.

So I rode it around the block a few times and it seemed to run fine. When I got it back in the garage, I blipped it a few times, when suddenly the rpm's stayed high even though I closed the throttle. I quickly hit the kill switch to turn it off. I took the top of the carb again, and made sure everything looked good. The throttle seems to open fine, and then snap closed like it should. I started it back up, and it was idling normal for a few seconds... Then it started buildig rpms up on its own w/out me touching the throttle and I had to shut it down again. Any ideas??

 

[Tom68]

Air leak, manifold or pipeflange spring tag cracking off pipe, try fattening up your air screw.

 

[KTM Mike]

Sound like Tom68 covered likeyl causes of the increasing idle speed -

While I dont have any specific experience with the 08 KTM's, the older KTMs I have had (97,00, 03, 05) all responded better to jetting changes with the pilot or a different needle. What sort of throttle position riding where you doing when it fouled plugs? If it is below say 1/2 throttle - the main jet may not be where the problem was. If you ride tight woods - most riders spend very little time on the main jet actually. Try a smaller pilot. If trouble spot is really tight tight slow woods, like 1/8 throttle sort of stuff - different needle may be in order. Different needles on my 00 300, and my son's 03 200 made a huge difference. Do some searches on KTM talk as well - there is a sub forum specifically devoted to KTM jetting.

 

[YamaB]

By building up idle fast I mean a FAST idle. As in 1/2 throttle open kind of rpm's... I did find that my slide wasn't closing all the way, so I adjusted the cable so that it would. It seemed to be running better as I rode it around the block a few times, but then the throttle stuck (grip twisted back, but the rpms stayed up there) and I had to shut it down again...

I think I am going to just take it to the dealer and let them sort it out... I hate spending the $$, but also don't want the throttle to stick and send me into a tree...

I race hare scrambles, and although there is a fair amount of tight stuff, there is also plenty of WTFO throttle on our courses. The plug has never fouled out during a race, but the bike just won't start the next time I use it until I put a new plug in. When I pull it out, it is black...