XR250L Carb Mod That Really Works
OK fellas, I think I have this figured out....

No pics because the digital camera scrambled it's brains when I rolled downhill with it in my fanny pack after unsucessfully jumping a stump last week.

Anyways.....get your bike into good light and slowly open the trottle. Watch how the mechanism works on the right side of the carb.

What you will see is that as the throttle opens, a small spring (up at the top of the linkage) pulls back the arm that contacts the accelerator pump. (the acc. pump is the small brass rod with the black rubber accordian boot protecting it....it leads down the a flat diaphragm in a housing on the bottom of the carb next too the float bowl)

As the arm rotates it pushes on the rod and this pushes on the diaphragm squirting fuel into the carb intake.

Now...if your bike was like mine (a 94 XR250L) you'll see a gap between the tab that touches the acc pump rod and the rod when the throttle is closed (0ff) all the way. So the throttle must be rotated a ways before the acc pump ever comes into play. You'll also see that the weak little spring stretches....stretches...and stretches some more before it gets enough tension to rotate the arm that makes the acc. pump work.

So...to fix it.

First get a good set of needle nose pliers a clean garage floor and some patience. Observe how the spring is fitted into the linkage...take a digi picture if you're forgetful. Remove the small spring.....removing it is the EASY part.

Study the spring and observe how the two ends are hooked and how they are oriented to each other.
Take a pair of small wire cutters and cut about 40 per cent off the spring. Use the pliers to bend the last coil after the new cut to form a hook oriented in the same way at the old one.
Replace the spring. This is WAY harder now because the spring is shorter and has to be stretched to get it to go on.

If you shoot the spring off the bike more than twice remember than when cursing the curse word comes BEFORE the other words (This is the reason for the clean floor...so you can FIND the spring after it launches) If you're trying to do this outside on the dirt or in the grass you're gonna be very angry.

I was able to work the spring back on with the help of a very small screwdriver to stretch it back over the rear part of the linkage. You have to do this to understand what I mean.

OK.....now open the throttle and you'll see that the spring now pulls harder on the acc. pump linkage and the pump rod gets shoved down earlier and farther than before.

Next you can take the "play" out of the system by gently bending two tabs. One tab is at the top of the linkage and contacts the arm that works the acc. pump linkage. As you close the throttle, this tab pushes the acc. pump linkage forward. You can bend that tab back to the rear of the bike to decrease the play between the acc. pump linkage and the acc. pump rod.

You can also bend the tab that contacts the rod down just a bit to take the play out of the system.

Whew.......long description.

It bloody well WORKS though...

I had a slight hesitation after carb and airbox mods that no amount of fiddling with the pilot air screw would fix.....this took care of it and the bike pulls much better from slow speeds and off idle.

No real Power gain just a big improvement in throttle response. Probably at the expense of a bit of fuel economy....but that's probably negligible.

I didn't pull the carb off to see how far the acc. pump squirts fuel now but the motor is happier and that's what it's all about anyway.

Enjoy

Ray Stedronsky
Davis, CA