02 KTM 400exc.
175 main
85 pilot
Runs fine with the choke out but as soon as I turn it off, it slowly flames out. If I try and "save" it with the throttle, it backfires(pops). Bigger pilot?
I have tried many different positions with the fuel screw. Checked float level per the manual. I just put a new float needle valve and seat in it. I took the fuel screw all the way out to check the o-ring and all looked well.

85 PILOT? I don't think so....

Your pilot jet, or the passage above it, is clogged. Put in a NEW pilot jet.

sorry, you're right..50 pilot . I will get a new one and try that thanks.

You can clean them out using a real small wire or aft end of a really tiny drillbit.

Just be carefull to not scratch them.

Sometimes soaking them in carb cleaner will help if they are really plugged bad.

I realize this thread is old now, but I had a 2002 400 EXC and a 42 pilot worked best for me. Don't try to clean it out. Buy a 42. If that works well for you buy a handful of them and have them as spares. They are cheap and the gas these days seems to turn to varnish and clog them easily. Please do not try to clean them with a wire. The hole is simply way to small for this. This is a very precise metering device. Even if you soak them in laquer thinner and have some success, you will never know if some of the varnish still exists in there. Even a small amount can make your 42 pilot seem like a 36 and so on. It is best to replace them when your bike becomes symptomatic of pilot jet problems. I hope this helps. -Paul

So now I am having the same issue on my 07KX 250F. I put a brand new 42 pilot jet in. It starts and runs fine with the choke ok but as soon as I turn it off, it dies....the same as if I hit the kill switch! Any thoughts?

ktm292, on 16 March 2012 - 08:10 PM, said:

The passage above the pilot jet is still clogged, or, hot start is stuck open.