I recently purchased a 2007 KLX 250 (paid $2300 - N. Florida) with about $1800 miles on her. Obviously, its been a while since she's been ridden consistently.

I've scoured the board and haven't found this topic covered... so here goes...

she doesn't run smoothly when the fuel line is set to "ON". She runs like a top when fuel is set to reserve, but set to "ON" and she sputters, stammers and stops.

Before you ask... the tank is full of gas.

Any ideas on why this is happening?

I was thinking that maybe the "ON" and "RES" are crossed and I have a little water in the bottom of the tank... or that possibly the "ON" fuel line be clogged.

Thank you in advance for any advice!

 

You're correct; this isn't a common problem.
I doubt it's water in the tank, but could be. One line could be blocked and the blockage could be in the tank on the pickup line.
Pull the fuel line from the carb and observe flow "ON" and "RES."
I suspect you'll be tearing some part off for inspection and cleaning. Get some new fuel line.

Welcome to KF and good choice on your bike. 2007 is the second-best year of the KLX250s!

 

Likely the main fuel line has been pinched. It's a pretty short run from the main to the stopcock, so easy for a weakened hose to kink.

I had this issue for a while after swapping to a Clarke tank. I decided to replace the hoses with just some straight fuel line from the hardware store, and the dramatic curve would always result in a pinched main line after a short ride. Eventually, I had to use cinch ties all along the line to ensure it would not kink.

 

I actually got some fuel line and a 90 degree plastic vacuum bend at the local auto parts store, no more kinked line on mine. The OEM line was folded and nearly cracked in two. Definitely recommend doing the plastic 90 to eliminate it.

Sorry, no pix. Maybe another day, but it ain't nuclear physics or anything.

 

I had the same thing when I got my KLX last July. I would run out of fuel in the on position, but run okay on reserve, The problem was the previous owner had the fuel lines kinked under the tank. They make such a sharp 90 degree bend that routing and length are critical. I replaced the kinked lines with good quality rubber fuel line. NOTE: After reviewing a parts diagram, it shows the OEM "on" fuel line is pre-formed. I made my own, but I did test fit and alter it several times before getting it just right. Good luck!

 

Happy New Year, all.... thanks a bunch for the quick replies!!! I think you guys are spot on with the kinked line. I actually noticed the line was in the wrong place when I was looking it over to buy... moved the line, but it's still bent and I can see where that would restrict flow. Never considered that would be the issue though.

Thanks again for the input. Will replace the line as suggested.

 

1/4" 90 degree vacuum fitting:



Around a buck!

I didn't need clamps either.