Jetting

Straight from FMF:




Main Jet 172 Pilot Jet 42 Needle OBETP Needle Position 5TH Power Jet Air Screw Fuel Screw 1 1/2

Jetting specs change with weather. Hot/humid is rich. Cold/dry is lean.

Personally, I'd go to a 45 pilot and try about 2 out on the fuel screw. That's typical lean pop. Symptom of too lean pilot circuit.

However, your main seems mighty fat for 90 degrees plus. You'll probably get a better rev and more pull if you drop to 175 or even 172. Just make sure you go back when it gets cool out.

Forgot to mention, be sure and check all your connections in the exhuast. Make sure you have no leaks around the header and at each joint. This will also cause one to pop severely. I've had to use aluminum foil to seal the mid-pipe joints before on some FMF systems but the newer ones seem better.

Just going to recommend the same thing about ANY kind of exhaust leak as a potential first culprit. Check every joint in the system. There are a number of really basic ways to do this.

I wouldn't be shy to try one number up on the pilot. Your fuel screw and particularly your needle setting are at the extreme side of rich as it is.

What is your hot start setup and have you checked to make sure it isn't in the open position?

Keep us posted as you work off this little hiccup. It's always nice to know outcomes.

Sometimes you can get a decel backfire if you have a air leak at the exhaust at the head pipe.

Put a smaller air jet located in the bell mouth of the carb in it.

They usually come with a #105 (CHECK FIRST) put in one step smaller (i.e. #100)

The KTM's pop.. don't try and jet that out with the other jets, like the pilot... you'll get rid of pop... but then the performance will suffer and be hard starting when hot