2007 Yamaha WR 250f Re-Jetting

This is a customer’s bike that had some serious carburetor issues.  It was having trouble starting and coming off an idle, but eventually got so bad it would not even run.  I went into the carb several times and did find some clogged orifices that once cleaned, caused the bike to run a little better, but the main problem was 2-fold:

  • Bent Needle.
  • Bad gas.

The WR comes with a non-adjustable needle, so I removed the bent one and installed a new yz-style adjustable needle.

It’s surprising how fuel can go bad so quickly and can even come from the pump bad.  Also, there was no “bad-fuel” smell when smelling the fuel in the tank, but I am certain it was bad because after correcting the needle and jetting, I installed my YZ tank onto the WR with fresh race fuel and it ran perfect, but when switching back to the WR tank, would not even run.

So after draining the fuel, re-jetting, and installing some new fork seals, this bike is ready to go.

Here is the jetting that worked well for me:

Elevation:  2500 ft.
Main:            175
Pilot:               42
Leak:               40  (this helps increase the initial squirt of fuel from the accelerator pump, and decrease bogging)
Air Screw:     2.0 turns out.

Author: joedean

Share This Post On