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More help needed. Jetting & High Altitude

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Ok folks I’ve got still got a bit of a problem with my jetting. I battled this last year when I first bought the bike from the owner in Colorado. Here are my specs.

2008 SM

FMF Megabomb header

Scorpion Muffler

3x3 Exactly

6,100’ in Elevation

I’m running a DynoJet kit: 150main, clip in 2nd notch of DJ needle, 22.5pilot

½ turn out on Keintrech fuel screw

I tried a 140main, clip in 4th this last summer and it was great on the bottom end but stumbled and fell on it’s face on the top end.

It runs great when accelerating (either slowly or quickly) from a closed throttle until about ½ to ¾ throttle. During the ½ to ¾ throttle portion of accelerating it will stumble then surge then stumble to the point of sounding like it’s going to die. If I continue to roll on the throttle it will snap out of it and continue pulling hard in WOT. I’ve found that the longer I hold it in the middle of the stumble/surge, it will take longer to snap out of it once I roll to WOT.

I’ve also found that it does it more often when I get turn into a strong head wind. I can only assume that this means there is more of a load on the motor (yet it’s not lugging or too low in the RPM’s) or that the strong head wind is some how getting to the 3x3 on top of the air box and giving it hell.

One more thing, when I turn the fuel screw in all the way while it’s idling, it will stumble a bit and continue running.

Is my problem in the pilot jet and not the main jet? :thumbsup:

I’m probably leaving something out in this, so if you can think of anything please post it.

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which dynojet kit is it?

Sorry, but I'm not sure. The PO had it prior to my buying it. I can only ASSUME that it's the stage 2 since it had the 3x3 cut at the same time.

I have the remaining "kit" which consists of main jets 132, 136, 140, 146, 150, & 160. The needle in the carb looks like the one in the DJ pictures and has all the stock washers in place per the DJ instruction sheet I printed off their site.

Eddie, I was reading through my notes and last year you had me tape off 1" of the 3x3 and test. Per the notes, it made it feel a bit worse with the tape.

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Today it ran great. Nothing was changed except a distinct lack of wind today.

Any other ideas out there?

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