It seems you should be seeing 70MPG plus or minus so hopefully you'll find something "wonky" once inside the carb.

One member reports no meaningful loss of MPG running my max power CVK setup (DJ140/2N, lidless, slip-on, near sea level, etc etc) when ridden for economy.

 

I found changing the needle makes a bigger difference on MPG then the main jet. I have run 132 - 124 main jets. Just went from a 124 to 128 with no change in fuel consumption ,but changing the needle from 4N to 2n was the way to increase MPG . I ride almost (missed 20 days in the past 2 yrs)every day all year so any change in MPG was a welcome one.

 

I've gotten better MPG the higher I go in main jets, weird. Started at 45mpg with 126, now at 50mpg with 132. It's normal to get less MPG here with bad quality gasoline and 5k feet ASL. I ride it very hard every day in heavy traffic.

 

Doesn't surprise me. Lean jetting will be less efficient, just like too rich, making for less mpg. Same can happen when you try to run too low an rpm for engine tune. As I said, we saw that with Gold Wings where trying to lug them too much would cut mpg severely. Honda said run 3000-4000 for max efficiency on them, downshifting as needed to get the best. We experienced that on a longer back country ride where we spent a fair amount of time in 4th gear, but still maintained 50 mpg.

I would guess the KLX250 is best round 4000-5000. My 650 is between 3500-4500, getting 60 mpg almost regardless of time in a lower gear or the type of riding.

 

Sorry for ressurecting this post but I'm a relative newb when it comes to my KLX250s. I just purchased a 2009 with 2300 miles on it. All stock. I plan on changing my air filter to a no toil, Slipon exhaust (most likely the FMF) and other bolt on stuff to get a little more performance out of the bike. I live 66' ASL.

My main question is with the filter change will I need to rejet the carb. I've read alot of people have had to rejet after changing to a better flowing airfilter, but they all seem to live and ride in the higher elevations. With living basically at sea level could I get away with changing the filter and rejet when I add the exhaust?

 

The bike will run if you do not rejet the carb. But, you'll want to rejet if you want better running, better starting and more power.

Since you haven't bought anything, just follow a cookbook that someone else already figured out. That is, just copy someone else's formula.

 

Thanks.

 

The good news is rejetting isn't that hard. I am not sure you really need much more than good Phillips and flat head screwdrivers. Just have a clean space to work in and ample time to do the job. There is nothing to it.

The KLX is a bike that makes solid gains when rejetted. It's really worth doing.

 

You really should start with getting either the DynoJet 2152 or 2206 jet kit. At the same time, order 3 extra DJ main jets - a 136, 140, and a 144... Then, at your altitude, you will have everything you need to properly setup/tune your CVK to properly fuel any and all performance mods you do on the bike - forever.. Just post your lastest mod and we will know which jet and needle clip position you should use..



Now, as to which kit to get - If I knew then what I know now, I would have gotten the 2206 kit.. So, if you plan on eventually going with a full exhaust system (Header and matching slipon - FMF or otherwise), I would get the 2206 kit. BTW, the 2152 kit can be replaced with the 2206 kit but not vice-versa as the 2206 kit will have you drill the slide lift hole - a "permanent" modification..

 

If you are changing to another foam filter, which I believe you are, it should make virtually no difference. If your bike is running lean or rich it will stay lean or rich. Most all foam filters will have about the same restriction. A K&N would be another story, since they are freer flowing - but not the hot ticket for off roading in a fair amount of dirt/dust. Foam is best there.


As said, if you look around you will find some good information. If you do Dyno Jet, KLXter has good information. If you do the Kiehin parts from Kawasaki or any other source there is a document on cheap KLX mods in my signature where the rider did some exhaust work and has the Kawasaki part numbers for the KLX300 adjustable needle, pilot, main and other bits/pieces necessary.. All depends on what you use.