TM33 Pumper Carb Jetting
 

I picked up a slightly used Bill Blue TM33 and installed it the other day. The jetting it came with is Pilot 37.5, Main 137.5, Clip in the middle and AF screw 1-3/4 turns out. I'm not sure if this is considered "stock" jetting for sea level, or what. The seller lives in SLC so he's around the same elevation as I am in Reno (4500').

My bike is a stock KLX250S with a Twin-Air filter, no snorkel and KLX300 exhaust.

Any ideas where I should be starting?

Rob

Well I know this much after a ride yesterday... it's a bit lean. At WOT in 6th going up a hill here in Reno, I felt a little lean surging. So in the next day or so, I will put in either the 140 or 142.5 main jet that I got with the carb, and probably the 40 pilot too.

What I was also noticing is that after riding and coming to a stop (e.g. a traffic light), the RPMs were up around 4000 RPM and would stay there for about 1 min before finally coming down. I would also notice it when riding along in 1st or 2nd gear, and letting off the gas and then having to use the brake to slow down rather than engine braking doing its job. I'm not sure what adjustment controls this but it sure was annoying.

Rob

Correction... I've apparently forgotten the difference between a lean surge and a fat surge. I welded a bung onto the header pipe and hooked up my wideband O2 sensor and discovered I was WAY rich.

I ended up with a 135 main, 37.5 pilot and needle in the middle position and it's at 0.7 to 0.8 Lambda (ideal is 0.8 to 0.9). For those that don't know, 1.0 is considered perfect (14.7:1).

Because of being so far, I also managed to foul the plug a little because I had a high RPM miss. A fresh plug and the miss is gone.

Rob