New XR250L - Few questions about jetting etc...

Hello all,

I recently sold off my old SV650 and picked up an older 1994 XR250L to commute with. This is my first dual sport ever, and I've got to admit that I'm having a hell of a lot more fun than I thought I would. Speed bumps are jumps. New developments and construction sites are temporary playgrounds. It is ridiculous, like I'm riding a mountain bike with an engine. This thing is ridiculously easy to throw around. Granted I won't be able to partake in any track days and there won't be nearly so much knee dragging as there was with the SV, thus far I have no regrets. Totally different kind of fun on the XR. Took me a little bit to learn how to kickstart a bike appropriately, but the XR seems to start pretty easily. Much easier if I lean her way over sideways, and then try to kickstart.

Anyway, there are quite a few things I'm working on sorting out right now. Needs a new front tire and tube, as well as levers which should arrive later today. Spark plug in that mix, too. Valves will be checked / adjusted this weekend.. Oil and filter have already been changed. (Idiot owner actually had the filter in backwards, thus oil was bypassing it completely. Luckily he had only changed it a few weeks prior and ridden it just a handful of times since then.) Over the next few weeks I'll also replace the fork oil, fix some minor electrical issues with the indicators and so on... I have a copy of an old XR250R manual, so most of the maintenance issues should be cover within that.

My main question is in regards to the jetting, however... The float bowl gasket seems to be leaking on this bike. I know that the previous owner screwed with it, but I'm not positive how much of a mechanic he was. Maybe it just needs cleaned and reassembled. That said, I'm curious about how to set up the carbs on these things. I've searched plenty, and I'm aware of the R needle compatibility and the spring mods, as well as switching outright to the R carb. I'm on somewhat of a budget, so I'll probably stick with the L carb for the time being.

This bike is primarily used as a commuter for me, so I'd like to keep it as fuel efficient as possible. That's a rather important item for me to mention. Last tank gave me about 70mpg, and I'd like to keep that, or damned close, if at all possible.

I am aware this bike is lean from the factory. The previous owner did install a UNI air filter, so I am assuming that is making it even leaner. My questions are as follows...

1) Gordon's Mods on an older XR250L - what kind of fuel economy drop occurs? Most riding will be cruising 45-55mph on city streets. I am aware off road / play mileage will be less, but I'm curious how cruising mileage would be jeopardized.

2) Assuming the mileage drop is too much, what sort of jetting would you guys recommend if I leave the snorkle as is, and don't change the exhaust or header? Just UNI filter. 125/40? Stock is 122/38 on these carb, and I believe the jets are stock.

3) Are the changes that would come with removing the snorkle and rejetting appropriately absolutely worth the mileage drop? If the exhaust is left stock, which I do enjoy for the stealth factor, is it even worth the snorkle changes anyway?

4) Can't even loft a first gear power wheelie with this thing D; Would slight changes like a tiny jetting boost and pumper spring help change that?

Thanks again for all of the help - very much appreciated!


You can go one size up at a time on the main jet, test ride at the highest altitude you will ride, wide open throttle, until it bogs being too rich, and go back one size or two. That's the best way and the safest jetting you can get. For the pilot, play with your fuel screw, you'll find info on other treads about that, but you surely can go up one size.

I've ordered a 40 slow jet and a 125 main jet. Near as I can tell, given the (lack of) mods that I'll be running, aside from that UNI filter, that should be sufficient to cover the proper jetting.

Checked the pilot screw, which the previous owner had already turned out... It must be at 4-4.5 turns or so! Incredible. Screwed it back in a little bit, and it dies if any gas is immediately given. Hopefully the new 40 size main will clear up that problem. Furthermore, the float bowl gasket is leaking pretty badly, so I've likely got some kind of vacuum leak in the carbs as well. New gasket is also on the way. Once all of that stuff gets installed, I'll report back with the outcome.

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