Need Baseline Jet Sizes

I'm getting ready to tear into the carb on a 00 650R that I recently purchased and would like to know what the stock jets would have been on a sealevel bike (socal). I want to find out if the previous owner rejetted it and how much. any tips on what jetting to run with a very open header and exhaust system.

By the way, is popping on deceleration a sign of pilot jet thats too lean?



Hi. Stock jetting on a completely "stock" XR650R for all 50 states is: 125 main, jet needle at 2nd position from the top. The pilot jet is fine, stock, or you can go up one if you have hard starting or low speed overheating.

With open headers and free flowing silencer, make sure you replace the stock intake boot with the competition one. Also remove "both" airbox restrictors, being the snorkel and the restrictor plate. Replace the main jet with a 175, replace the jet needle with the competition one, set it to the 3rd clip position, and leave the pilot jet alone.

Popping while decelerating is normal and does not mean your pilot is lean, if anything, it's because of a rich condition allowing fuel into the exhaust, but this is normal and should not be tampered with. A stock YZ426 pops like that also, it's not a problem.

Keep in mind that high performance 4-strokes MUST run quite rich in order to produce that awesome power.

Just remember! Lean jetting does not cause popping, as there is less fuel to cause a "pop". And lean jetting causes overheating and lack of power also.. so avoid it. The bike is jetted lean only to meet EPA standards, that's all. If you have heard of the XR overheating at low speeds, you should also know that Jetting the bike properly as stated above, will eliminate overheating completely, as long as you don't idle for very long.. The bike was made to ride, not idle.

Hope this helps.



Thanks, thats a big help knowing how far off of the stock settings I am. I am surpised they run such a lean main jet(125), must be because it doesn't need much gas with all the epa crap they put on the bikes now. :) At least they make it easy enough to tear out! It looks as if the previous owner did the required surgery for me.

Glad to hear the popping is normal, slightly new to the thumper scene so I thought it must have been jetted wrong!

Thanks Again


Many people mention going to to find out how to uncork the bike properly, but he likes the needle clip in the fourth position, not the third, and he advises to change the stock pilot jet from a 65s to a 68s.

The kit from Honda doesn't come with a pilot jet(i think) and it says the 3rd position too.

What is best?

Well, I have tried them both, the 3rd and the 4th, as well as the other pilot jet. I found the 4th position, and I was using the competition needle, not the stocker... Anyway, I found better low end and lower midrange power with the 3rd position. I could not tell any difference with the other pilot jet, other than slightly easier medium warm starting..

:) I bought a XR650R 2003 last year (September 2002) and have since opened her up with the HRC kit minus the high compression piston & cam. The specs published on are dead on for sea level. I did not replace the radiator cap (and would not recommend) because once I opened her up and installed the #68s slow jet I have not had any problems with overheating. I currently run as follows: Main = #175, Slow = #68s, Jet Needle = 4th groove from the top, Pilot Screw = 2 1/8th turns out. Please note that these are Honda OEM jet sizes. I have heard that Honda does not follow the same size standards as other manufactures.

The factory jets are as follows: Main = #125, Slow = #65, Jet Needle = 2nd groove from the top, Pilot Screw = 2 turns out. (California Pilot Screw = 11/2 turns out)

BTW check the Air Cut-Off Valve on your carburetor. Its sole purpose in life is to keep the bike from popping on deceleration. The factory jets them so lean they need to put a little extra fuel in the cylinder to keep things smooth during deceleration.


Good call on that carb line, I'll have to check it out. I have since installed a 175 main and 68s pilot and it is running much better. I combined it with a the jardine header and exhaust, it made a huge difference. I don't know why but the ProCircuit system popped alot more on decceleration. The jardine is quite abit smoother as far as the exhaust note. Power feels about the same as the PC setup, maybe a little more power off the bottom. Fun as hell, I have rode motocross bikes for the past eight years and I quit racing and got this to play around on. I'm pretty impressed it is a very fun bike to ride long as you don't try to jump like I used to. OUCH! This thing comes down like a brick. I should have known better but, you gotta try everything at least once! :)


Mine flies well, but lands hard also. I was thinking I could ease up the hit if I went a couple of clicks out on the compression dampening. I guess compared to a MX bike the BRP will land hard no matter what you would do. Anyway, that Air Cut-Off Valve has a tiny U ring (Honda’s word, per the shop manual) right behind the diaphragm. If the diaphragm is in fine shape look at that U ring closely. I don’t have an aftermarket pipe on mine, just the HRC tip. No pops during deceleration at all. Have you adjusted the Pilot Screw? How is it just off idle if you crack the throttle?

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