Try leaning out the air screw by turning it counter clockwise a quarter turn at a time. If the air screw has no effect, install a leaner pilot jet and return the air screw to 1 turn out. Proper air screw settings are usually between 1 and 2 1/2 turns out.
1997 300 mxc manual says 40:1 to 60:1 i find with the stock carb settings my bike runs just right at 50:1
It does not. My 09, as well as all other year KTM atvs, have a carb. Same goes for the 500's.
take off the carb. on the botoom of the carb is a bowl take screwsa out and the big jet in the center is the main jet. remove with a flathead screwdriver
A single cylinder 2 stroke 249cc engine with a Keihin PWK36 carb.
Got this off of KTM talk, 44HP for a 450 exc.
KTM recommends unleaded fuel with 91 octane rating.
70 stock
2005
.7L
Sounds lean to me. I would check these things out, make sure that the air filter is clean, put in a new plug (gapped properly), drain out the old gas in the tank and put a gallon of fresh 91 octane. Now try the bike, if it is still backfiring, I would pull the carb off and clean it thoroughly pulling the main jet, pilot jet and check what position the clip is in. I would check the owners manual for stock carb settings (if you don't have a manual get with your local KTM dealer) and adjust the carb back to stock. If you are in a higher altitude, check with your shop and see what they are running in their bikes for mj, pj and clip position.
.5 L