Jetting question for 02' XR650L

My first post... I have always ridden red and now I own the heaviest dirt machine known to man...that is not John Deere green...

I plan to do the basic mod's which have been tried and true by you guys on this site. I plan to start with the intake mod's, like slide drill, snorkel removal, uni filter, and jetting. I will wait until later to modify the stock exhaust. I see a lot of guys listing the 55 pilot jet/158 main jet combo, but it seems most apply this with an aftermarket exhaust or stock with mods. With everything but the exhaust modified, is this still a good combo or would it be too rich? It seems like it would be a little excessive without the exhaust mod, but I am not sure how lean it runs from the factory. I have seen quite a few comments of guys leaving the stock exhaust alone as they say that the power increase is marginal for the price.

Any feedback is highly appreciated to save me some trial and error. I look forward to getting on the team in the future, it is a great site.

I live about 10 feet above sea level, and using the stock exhaust and all the above mods I run the BD 58 and 160 jets. It runs well.


If you wanted to open up the stocker you could pull the core. Grind the two spot welds. Remove the 2 bolts and pull the core. You can always reinstall for the stealth missions with the two bolts.

P.S. I run 158-160 (Still playing) and 58 But I am running an E-series exhaust

Better to run a little rich than too lean. These bikes are leaned out from the factory before they hit the showroom so with the intake mods a 158 main & 55 pilot would be good start. Jets are relatively cheap so if you're even thinking about exhaust mods pick 2 or 3 mains so you can experiment, yes, trial & error. Too many variables and every bike is different and there is no magic formula.

the DynoJet kit for my 2001 XR650L came with two mainjets, a 162, and a 165 ... the 162 was recommended for the stock exhaust, (which ran perfectly for me), and they recommended the 165 for aftermarket exhaust, (I have installed it, but not ridden it yet) ... my usual riding area varies from 2100' - 5000' ... and with the other uncorking mods, seems to run great ... I'm very satisfied with the stock carb, .. hope this helps some

Hi Guys. Something to keep in mind hitorq, the dynojet jets are there own numbering system, different from the keihen jets that are stock with the machine. As I recall they are a little higher number for about the same opening. I just jetted my L last weekend and a 55 slow and 158 keihen jets should work for you provided you take out your baffle and do all the other normal uncorking you talked about, if you don't remove your baffle it will be too rich. Mine was so lean from the factory that it wouldn't run without the choke for about 5 minutes and then it backfired and farted around even with the baffle in it. I went on to add a e-series s bend pipe with 12 discs and went to a 160 keihen main jet, once again it was very good and real good power. What a difference from stock. I'm at about 2000' elevation. Hope this helps and welcome to the forum, its good to have another member.

thanks for that info ... I was wondering why my numbers were different from most in here ... you would think something like that would be standardized, oh well ..

As I understand it there's different ways to measure it. By hole size(mikuni) or by volume of flow allowed per unit of measure(keihen) and I don't know what dyno jet does but its different from the others. Nothing like confusing the issue for the rest of us, huh.

Thanks for all the information, I was just about to inquire about the difference in numbers for the two jet makes. Usually this does not occur between companies, so I this clears it up. I will probably start with a Keihin 155 if I leave in the baffle. Is there a dramatic sound difference with the stock exhaust baffle removed? I assume it is just wrapped in fiberglass or some other wrap? Looks like a quick spot weld grind and two bolts to remove. I am ready to start tearing into it, as with everything that enters my garage...

Funny you should ask about the sound difference. Now I'm gonna sound a little geeky but here goes. I noticed a 6 decible difference between the baffle in and the baffle removed. 92 db at a 45 degree angle 6' from the right side of the pipe at about 3000 rpm. 98 db with the baffle removed but the tone dropped to a real nice sound as you'll soon find out. When I put my e-series s bend pipe on it went to 104 db, a little louder than I like but the low end is better than I had hoped for. Jetting also changed a little but thats another story. Hope that helps, now I'll go back and read some more tech articles or something, whatever geeks are supposed to do.

Thanks again. I will have to give it a listen. I spoke to a guy at xr's only and he stated the stock exhaust is VERY restrictive and that jetting changes without pipe mods would only over richen the mixture. This makes sense to me, but it seems like there are several folks on this site who have enjoyed a pretty good power increase with the jetting/intake mods while keeping the exhaust in stock form... My only assumption is that the stock exhaust is pretty restrictive but still has a small potential for increased air flow from the intake mods alone, being that it is currently too lean to start with... Anyway, any other comments will be helpful, for shortly after this it I will stop writing and start wrenching. More to follow...

Where does one get a 55 pilot jet? the parts diagram does not show a part # for the 55 pilot jet, just the 50 pilot. where are you guys getting the 55 pilot jet.



Xr's Only,Sudco, or carbparts can help you out for the Keihin pilot jets, among others. They all have websites.

Anyway, any other comments will be helpful, for shortly after this it I will stop writing and start wrenching. More to follow...

Just be carefull when you are removing the slide. That rubber diaphram is very thin. Also, clean and reclean the slide and diaphram after drilling the 2 outboard holes. Shimming the needle is fairly simple. You just need a nylon or metal washer of the right thickness, ~0.030", and has the same outside diameter as the jet needle head. Hint, you can grind or cut the washer down to fit if its too big around.

Good luck & happy modding.

Thanks D/Dog. By the way, has anyone heard of using an ATC 250R insert in the exhaust. I was told that it would interchange with better breathing ability?

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