XR650L Big Gun Jetting

I just bought a 2004 XR650L with a full Big Gun exhaust system with the quiet insert in. It doesn't run so great down low right now so I'm thinking it hasn't been jetted properly. Any jet kit and/or jet size recomendations? Mixture screw settings? Anyone know what the stock size main jet is? I'm down at sea level and humidity is 70-90%.

I believe stock is 155. I am using the Dynojet kit which includes the 160, and 165 mains, new needle, as well as a lighter slide spring, around $50 for the kit. I am at sea level same humidity if not more have a FMF full system, K&N filter, desnorkelled and drilled air box, I am running the 165 main, with needle in 4th notch down and almost 3 turns out on air screw. You can save some $ by just buying the jets and doing daves mods.


Please note the dynojet jet#s do not correspond to keihin #s.

A DJ 160 is approx. a keihin 158.


I just did re-jet form a new exhaust system. I have the big gun header and WB E-series muffler. I am running a 158 main (actually I drilled my stock jet to 1/16" which is .0003" bigger) and 55 slow jet, also did Dave's mods(washer, drilled the slide) De-snorkled, de-smogged.

Stock jet is a 155 main, 52 slow.

Runs good, I had a little bit of popping on deccl but worked that out with the pilot screw I'm at approx. 2-1/4 turns. I would suggest starting with these numbers if you go the non-dynojet route.

A 58/160 is what worked for me at about 150 ft/sea level.

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