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TM40 Jetting Data


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I'm getting ready to order a TM40 for my XR650R and I want to add a handful of jets, nozzles, needles, etc to the order. My XR is uncorked but I plan to add the HC stage one cam.

Where can I find a database for XR riders with the TM40?

A friend in Colorado (w/stock cam) but at similar altitude suggested these settings:

Main Jet: 132.5

Pilot Jet: 22.5

Air Jet: 1.2 (important change)

Needle: 9DJY01 (important change)

Needle Jet: Y4 (important change)

Accelerator Pump Nozzle: 45 (important change)

My needle is set second notch from the top.

Anyone here riding mostly 5000-9000 feet have any suggestions?

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It's nice to learn how to tune a carb when you do these changes yourself. That way, you will be able to make changes based on personal observation, rather than anonymous forum contributors.

That being said, there is a lot of good info on jetting here. Just buy extra jets and try them out. I really don't think anyone is willing to guarantee that any particular jet suggestion will be the absolute perfect one for you.

I'm not trying to bust stones, just being realistic.

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When you order the TM40 thru Sudco, it's my understanding that you specify which jets, nozzle, needle you want installed.

I don't have a Mikuni tuning manual so I need some kind of reference point so that the carb arrives at my door somewhat close to being in tune. I'll have some extra jets above and below to fine tune it.

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I got mine from XR's Only and they jet it to your elevation. Mine came a little fat, but was fairly close. I agree with disabling the accelerator pump when dialing the jetting in. The pump on mine was way out of rig which is something you might plan on doing a lot of tinkering with.

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