Originally Posted by mustang

I agree that if it ran fine last year and now doesn't, you've got some dirt or varnish in the carb. When I was playing around with a TM33 on my bike, I ran into a similar problem. The RPM's would hang between shifts. Even revving it up in neutral, the RPMs hung a while before settling back to idle. When riding one day, I noticed that whenever I came to a sudden stop, the bike would stall - every time. It turned out that a piece of crud found it's way into the choke mechanism. Even though the choke seemed to be closed, it actually was still cracked open a little bit. After cleaning the choke out, it solved the problem.

If your pilot jet is indeed too small, one way to verify that is to crank open the the fuel/air mixture screw. If you have to open the mixture screw 3 turns or more from closed to find the lean/rich sweet spot, you need a bigger pilot jet. Open the mixture screw 3 or so turns from closed and see if it runs better - if so, then go bigger on the pilot jet. But again, I think you've got dirt somewhere.