400 exc gas mileage

I ran out of gas at only 75 miles w/ IMS 3.1 gal. tank on 02 400 exc in the desert! :) I noticed that I seem to be leaking fuel out of the vent hose from the bottom of the float bowl, is this the problem? :p What kind of mileage do you guys get? :)

I've only had my '05 KTM 400EXC for a month, but here is my mileage experience. When I'm riding on faster trails, I'm getting about 35 miles per gallon. When I'm riding the tight twisties, and doing steep hill climbs, where I'm riding a lot in higher rpm's, I'm not even getting 30 (I hit reserve at about 47 miles). Hope this helps!


I feel your pain my friend. I have an 05' 450 EXC and I went to reserve at 31 miles. That's right 31 freakin miles with 2 gallons of gas. I hope you solve your problem, me on the other hand I may throw a match to it. If any of you are riding the Arizona National Enduro and see a KTM on fire at mile 31 that will be me. I picked a bad day to stop drinking.........James

I have an '02 400 EXC and I get around 35 mpg on mixed riding. If I'm on a lot of single track and really hammering it I drop down to 25 or so. I've goten as high as 49 on long easy dirt road stretches (San Felipe to Gonzaga).

From my experience you could really just be getting that 25 per gallon. You can save a little fuel by shortening the "squirt" from the accelerator pump in the carb. There have been several threads on how to do that, I've done it to my bike and it helps with the mileage a bit, and really cuts down on bogging, especially at altitude. :)

I would start with, remove the carb and look in from the engine side and confirm that you see a 1/4" hole that goes thru the first layer of the slide. Occasionally this gets installed upside down and if so the hole is hidden at the top, when that happens they idle poorly and burn gas like crazy.

Next, you gotta have the JD kit, the engine will never be right until you have that!

Next would be squirt time on the AC pump, it is set at 3 seconds of squirt after you twist, if you ride aggresivly, rear tire spining most of the time I would shorten it to 1 second, it you ride mostly hooked up I would leave it at 3.

Based on your observation of overflow hose drool your float level is probubly a bit high, there is a hose that come out the bottom of the bowl, that is your overflow, I remove that hose temporariliy, wipe dry the top of the transmission case, then ride around kinda mellow for a couple miniutes, light bumps only, then check the top of the trans, if its wet the float level is too high. I adjust it down abt 1mm at a time until very little spills out.

When you put the float bowl back on the bolts on the bottom rear each have a tab with two holes for hoses, set the right one aside, use the left, that hose from the bottom of the bowl, put it back on, route it up around the fuel inlet, then down thru that tab.

Next the four hoses coming from the top of the carb (stupid engineering at its worst) if they get into water in a creek crossing gas can not flow into the carb, so look at where they come form, there is a "T" on each side near the top of the carb.

From the left "T" run one hose down like original, run one across to the right "T", shorten it to fit, run the other from the right "T" up and into the air box, find a piece of tubing to splice it with the one you nuked and run it all the way to the bottom of the airbox (if you leave it short and the bike lays on its side the filter may get its oil washed off, you want it all the way to the bottom. Now the bike will run thru streams, not quit if mud gets on the hose ends (this is why the ends are slit) and spilage when on its side should not get on exhaust which it will it you route them up under the tank.

Next item would be you need a fuel mixture screw that you can adjust, then when you are on a long fuel range sensitive ride you can lean it out a little, make certain you get a brass one, do not let anyone sell you an aluminum one. KTM hard parts, Scotts or Kouba all have nice brass ones, JD says he is going to have one soon, just say no to the one that starts with a "Z"! Aluminum rubbing against aluminum is a very bad combo and that carb body is very expensive!

I have gotten as little as 28 MPG and as high as 50 MPG depending on jetting and terrain. With proper JD jetting and +/-1 sec. AP mod, my average for ~12 rides is 39 MPG. With my MXC gas tank this should be good for 120-140 mile rides. I even went 110 miles one day without going on reserve! But also I'm no racer, I'm just a 50+ guy riding for fun and scenery. :)


I'm in the same class of rider as Durango Dave. Dave Hopkins (above) hit most of the items you need to check, i.e. the squirt duration, float level, and the needle position. When I got my 01 400EXC I was only getting 55-60 miles before hitting reserve on a full stock (2.3 gallon tank). That got old since all my riding friends ride KLX's which pretty much run forever on a gallon of fuel and 60 miles a day is nothing compared to our normal days in the mountains.

Anyway, I got the larger 3.1 gallon Clarke Tank and at the same time adjusted the float hieght which was set too high from the factory causing the fuel leakage you're describing from the overflow. I also "raised" the needle one notch to richen it up a bit since it was lean from the factory. Every since then I'm good for 80-100 miles depending on the terrain. I managed 103 miles when I hit reserve while riding in Moab 3 years ago.

Good luck and let us know how it turns out. Save your matches, you already spent $7K on a great machine that just needs a little TLC and patience to get things sorted out.


Good advice here.

The JD kit noticeably improved my mileage. The stock needle goes from being lean in the beginning to overrich in the midrange due to the taper. The JD has different tapers, and it resulted in much more responsive midrange with significantly better range on the bike for me. I was going to get a bigger tank but the new needle made it unnecessary. I get 40-50mpg, depending on terrain (and amount of time lying on my side :) ).

I'd check the float level first, and get a JD kit regardless of how much the float issue improved things. The squirt time might have an effect, depending on your riding style, but I doubt it is the big issue.

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