So I ran jets all the way up to 135. There was no noticeable difference till I went to 135, it started to run worse. I then went to a 100 and it ran much better, dropped the needle all the way down(top clip) and ran even better, adjusted air jet to 2 1/2 turns and would rev right up, not the quickest mind you but it did. I then moved needle clip to middle, but ran worse. I am very nervous about leaning it out. I had it jacked up to try and fine tune it while at full throttle, when all of a sudden the muffler started to smoke, not exhaust, but smelt like something burning. Could it be that the muffler has never been heated up, as it would never run with it in till now, and it was just burning off some paint?I pulled plug, and it looks hot. What next

 

Old saying is that if a 2 stroke runs great,beware, somethings fixing to blow... Obvious the jetting is too lean with a 100 main jet with the plug as white as it is.Go to the 130 and test it while driving it not while it's on stands or jacked up.Kill it while you're at speed and check the plug. If it's still white,still needs to go up on jetting. If it's a light or medium brown you're getting closer.

 

The problem I'm having, is it won't rev past 1/3 throttle with a jet any higher than 100, unless the muffler is removed. Also, this is a 4 stroke.

 

If I go back to a 130 jet, how do I adjust the air screw to get it to run, I'm at 2 1/2 turns out now with a 110. Nothing I do will get it to rev up past 1/3 throttle.

 

If so then sounds like the exhaust is restricting.Plus start back at the basics,valve clearance check and compression test. May not just be a carb problem only.Plenty of cheap clamp on mufflers out there that you could try also.If that doesn't help the problem may be ignition related.

 

Cut the back end off your muffler, gut it out as much as you can. Get an exhaust tip off eBay, and weld a flat plate back on the muffler, install the new tip, with a screen for flame arrestor. Get the tip first, you can probably cut a hole in the back of the muffler. I had a Polaris that would barely run, until the muffler gutting trick. Since then, I've done it to all 3 of my Arctic Cats, including the diesel. Once you've done the exhaust, remove air cleaner, run it at high speed and spray either Sea Foam, or a fine mist of water, yup water into the carb. That will steam clean any carbon out of the motor.