Have a scrambler 400 4x4, I have a flat spot when going real slow, if I hold the throttle in one position it hesitates, I have to keep on/off on the gas to loose the hesitation. The rest of the throttle is good, mid to top. Its just the low end. i was thinking possily needing a bigger piolt jet, or maybee playing with the air screw. The air box is modified and I have a high flow air filter. Any suggestions. thanks.

 

Have you tried moving your jet needle clip position (in the slide)?

One thing I've noticed over the years is that the 2 stroke polaris are bad about the engine vibration "rattling" the jet needle around so much to the point that over time they egg out the needle jet and and wear down the taper of the jet needle. Sometimes you can get around this by a simple clip position adjustment, other times it requires replacement of both.