Thanks buffallodan for putting all this great info together.
The stock TE610 carb comes with a blank leak jet on the accelerator pump, i.e. the leak jet is closed off and any imperceptible bump of the throttle results in the accelerator pump squirting fuel into the carb. That results in the bike lurching forward and becomes really annoying when stuck in first gear on a tight trail.
I tried to tune that out by modifying the throttle cam, that partially works but the real fix is to put a leak jet on the accelerator pump IMO. There is an excellent discussion by Clark Mason over at Thumpertalk
on all of the different methods to tune the accelerator pump and after reading that I became convinced the leak jet is the best way.
The leak jet bleeds a small amount of the accelerator pump fuel shot back into the carburetor bowl. So when you whack the throttle open some of the fuel goes through the leak jet and the rest into the carburetor. Changing leak jet size allows you to tune the pump shot duration.
The other thing the leak jet does is bleed off small little bumps on the accelerator pump. So when you are rattling along a rough trail and bumping the throttle 1/32 of a turn or less the fuel takes the path of least resistance through the leak jet instead of the longer path into the carburetor port. Works for me anyway.
I tried the 60 jet TE510 riders were recommending and thought that was a little to big for the TE610 with stock jetting. I have been using a 50 jet for several months now and am pretty happy but I am looking forward to some feed back from the real tuners here.
P/N 019-750 $8.80 US