Jetting Advice: '01 XR650L, Exhaust Tip, Snorkel Removed

I bought an XR650L with what looks like a Baja Designs or Thumper Racing exhaust insert. I'll take out the snorkel if it's not out already. It looks like a K&N filter (do they come stock with a pleated filter?). The smog stuff is blocked off. Right now it backfires a little when downshifting. I'm at sea level to 3,000 feet.

How should I jet it, and how hard is it to change the jets. This bike is for my brother in law, so I don't want to spend too much time on it. Maybe tweeking the idle mixture will help?

Thanks in advance,


You'll need to rejet & richen the fuel mixture since there is a slight mod to the exhaust, if the air box is opened up, and if there is a foam aftermarket filter installed. The pleated paper is stock.

Try #55 pilot jet and a #155 main jet. The carb will have to come off to replace these, along with the seat & tank, relocating the brake reservoir & taking off the exhaust header heat shield to get them out of the way. I've done it twice, but I've got the Factory Service manual so it wasn't a problem. :)

Call Baja Designs or another reputable shop that does carb mods routinely for the XRL. They should be able to help in determining the best jet sizes base on the mods already in place for that bike.

Good luck. :D

Just for reference, what's stock jetting? This thing runs decent, but I just want to get rid of the popping without too much trouble. I gather that they're typically jetted lean for emissions and because of the smog stuff and constipating factors like the pipe and snorkel.


I believe stock jetting is a 52 pilot and a 150 main. A 55 pilot is the usual setup for sea level and a 155 - 162 for the main. I had a 153 main and an XR's Only pipe on my L with the needle shimmed, slide drilled, and a UNI air filter. I had it dynoed at 38.3 hp. I have since removed the XR's Only pipe (TOO LOUD) and put on a WB pipe, because the sound and power band can be easily tuned with this pipe. I am also running a 162 main jet. I'll have to wait for the spring before I can acess a full evaluation. :) The stock filter is pleated FYI.

You didn't state the model year of your L, but here is some info from the service manual.

Stock jetting on the XR650L depends on year, frame serial number, California, and Canada.

The frame serial number is on the right side of the steering head.

1993 XR650L

49 state version frame s/n PM-000001 thru PM-000958 - 155 main / 152 in high altitude

49 state version frame s/n after PM-000958 - 152 main / 150 in high altitude

California frame s/n PM-000001 thru PM-000078 - 155 main / 152 in high altitude

California frame s/n after PM-000078 - 152 main / 150 in high altitude

Canada - all - 152 main / 150 in high altitude

94-04 - all - 152 main / 150 in high altitude

All years slow jet was 50

Just for added info, the float level stock is 18.5mm.

Hope this helps,

Mike in KC

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