Terrible Mileage

[kdxiowa]

I hoping you folks can help me out here. This is what I have -
The Cylinder and head were done by Fredett Racing. This included porting, polishing and re-plating (nickasil). A Wiseco forged piston was used during re-assembly. The carb was bored to 35mm from 33, the previous owner did that himself. The compression was raised most likely by using a thinner head gasket… I don’t think Freddett actually would have planed it down. Boysen reeds were installed and the carb was re-jetted to Freddett specs.This guy did everything Freddett recommends (to the Engine) except he went with the gnarly pipe instead of the woods one. I have only been able to get around 40 miles to a tank. Oh, my bike is a '98 220. The airbox cover has been completely removed. That's all I know of that's been done. Why such bad mileage??? :yikes:

 

[dsndblm]

From what I have read and from my experience jetting is different for every bike of same year, model etc. I jetted using someones recomended jets and my KDX was nothing but a blubbering, mosquito fogger!
How does your plug look? Is is smoking a lot? Have you checked your float level? I would check the float level first and then use Daves procedure from the KDX page and look at your plug readings. Also, do you ride the bike wide open a lot? If I take it easy I can get almost 70 miles out of a tank. It really drops if I am running the bike hard.

 

[kdxiowa]

Yeah, I've been on it pretty good but I didn't think it was too bad. I haven't pulled the carb off myself yet I'll have to look at it and check Dave's procedure on the KDX page. Thanks.

 

[wibby]

What kinda riding are you doing ?

When I ride up at Johns Peak with Carvr it is mostly tight and gnarly single track, may get out of 3rd gear once in awhile. Up there I probably get under 50 to a tank

But go to Prospect where it's mostly quad trails and lots of thick gravely roads and I get around 70 miles per tank, and thats wide open 3rd, 4th and 5th stuff!

 

[kdxiowa]

You're right, most of my riding so far has been 1st and 2nd real tight bar bang'n single track. I'm still getting used to riding a two stroke I was on a 650!

 

[crazymike]

any chance your tank is leaking? just an idea.

 

[kdxiowa]

Yup, checked that one too. Although, after I had to dremel off one of the bolts to remove the tank, it might leak now.

 

[marksharp]

Mileage

We've checked our mileage in different situations and concluded that although jetting is a factor, riding conditions make the most difference. Tight woods, 1st and 2nd gear,on and off the throttle use at least double the fuel of more open areas, 3rd gear and up. It only makes sense. Our last ride, combo of 2nd, 3rd and 4th gear, some tight stuff, but mostly quad trails, and fire roads etc, we filled up at 35 miles and it took less than a gallon. 2.8 gallon tank and we could push close to a 100 miles on a tank! that would be too close, but 75 should be no problem. You can survey your own bike as you ride, but I think it will be pretty close across the board.

 

[canyncarvr]

Both FmF pipe profiles are 'gnarly', so saying '..he went with the gnarly pipe instead of the woods one.' is unclear.

I presume the -30 or rev profile pipe is being used?

You cannot 'jet to spec' in the first place because bikes, riders and conditions vary too much. For sure you can't 'jet to spec' which takes one pipe into account and then run a different pipe and expect anything close to 'tune.'

The -35 (torque....or 'woods' if you prefer) runs much richer with the same jetting than the -30 (rev...or 'desert' if you prefer).

And the carb was bored by 'some guy'? I'm sure there aren't any questions about THAT! (That's a joke, son!) You don't bore a 33 to 35 on the center of the original bore for one thing. Was that done? What happened to the jet block height?

Porting varies as widely as you can imagine. Many different ways to do it, many different results. It is well within reason that a 'ported' KDX could be LUCKY to get 40 miles out of a tank.

Too many variables to give you 'the number' for that. I've gotten as little as 25 miles out of a tank...as many as 85+. And that was with the same bike, same rider, properly jetted.....just different conditions!

You won't know anything until this bike is jetted correctly. That's up to you. It's common for KDXs to be jetted rich. Mostly that is due to a no-wrench rider or just a rider that don't care. The single biggest 'bang for the buck' you can get out of your scoot is to properly jet it. If you think it runs well now (and it's not jetted correctly), getting the fuel delivery system sorted out will be a big surprise for 'ya.

Good luck!

 

[kdxiowa]

All the information I gave was what the fella I bought it from told me. I can only clame ignorance on what's really done inside the engine. The bike runs out real good once warmed up. Rips from the bottom through the top. I am new to two strokes so please be patient. I had a XR650 prior to this. I have no real complaints about the power, I just thought it would be a little more consistant on how much fuel it uses. Maybe that's my four stroke ignorance, I also have an XR250 but there's no comparison in mileage. Granted this is a bike not designed to cruise down the road but I would like to know how many stops to plan for on a long ride. :ride: :ugg: