125-200cc Slow/Strange Return to Idle

Hi Everybody

2012 WR 165 with KTM 200 pipe.

Having some issues getting the bike to run right following installation of the 165 kit. As you can hear from the first 20 seconds of the video, the engine exhibits a protracted, unsteady return to idle after the throttle is blipped. Also the whole response from the motor is off. It's whatever the opposite of crisp is. The engine just sounds off and "fluffy".

I know that unsteady return to idle is a classic symptom of too lean on the pilot circuit but this issue can't be dialled out by playing with jetting.

i have: checked for air leaks, checked the reeds, checked carb float level, fresh air filter, fresh silencer packing, fresh, correctly-gapped spark plug and tried different base gasket thicknesses. I tried VP race fuel in case its a fuel issue. Nothing answers.

Anything else anyone can suggest please? Timing? Help, I'm seriously considering putting the old 144 kit back on as I'm getting tired of messing with this thing!

Sticky / frayed throttle cable? Carb tight on slide for last portion of travel? Does sound like jetting though.

Take your carb off and ultasonic clean the body.

Sounds slightly lean on the pilot jet. What jetting changes have you tried?

Thanks for the replies and the suggestions everyone.

As for jetting changes, I went up a size on the pilot jet but it was really blubbery just off idle so I went back

Was the return to idle better with the bigger pilot? If it was then perhaps the richer pilot with a leaner needle might be worth trying.
Be sure you are taking note of throttle positions and not engine speed. "Just off idle" could be pilot and airscrew, needle straight section or even clip position depending on where your throttle is (1/16 through to 1/3 open).

What type of carb is it?

Does not sound that bad to me is there any hesitation when riding.