WR250F tuning question.

[Duwvesmith]

I am in the process of tuning my 2002 WR250f and would like some help from those of you who have maybe been down this path already. I have cut the "Grey Wire", removed the airbox snorkle, and removed the exhaust insert. I still notice a stumble in acceleration if I chop the throttle closed, and then open it quickly.

Other related questions are about jetting. What main jet, pilot jet are best, and what needle positions are most effective?

Thanks!

 

[bailey43]

What are you running for exhaust? Have you shortened the throttle Stop?
I own a 2001 wr250f did all the same things you did including the throttle stop thing. The manual recommends 95 octane or higher. Most gas stations can't even touch that. So I purchased some racing fuel and cut it 50/50 with sunoco premium 94 octane. This makes such a significant difference to the throttle response. IT HITS HARD!! And the lead found in racing fuels helps keep the valves lubed. Yamaha says its ok Too!
Good luck I haven't had the need to play with jetting. That and an exhuast are my next two steps.

LaTeR

:cool:

 

[webbrace]

I have a 2001 WR. Boozer gave me all the hot tips, (thanks). So far jetting is stock. I did the grey wire mod, air box lid, throttle stop, seat/tank combo, and pulled the cork out of the end of the exhaust. This thing is a blast to ride, It does have just a little stumble right off the bottom. Next week i am putting on a Power Core 4 exhaust, to see if i can get a little more snap out of it. I will probably go up on the pilot jet one size and the main jet one size and see what happens. By the way, This thing starts 1st or 2nd kick, hot or cold. I will let you know what happens.

 

[kmccune]

I've read posts on YZ cam timing making a big change.

Kevin

 

[BUCKWHEAT]

A stumble right off the bottom should be corrected with the pilot screw. A bog would suggest its too lean and a burble or missing would mean its too rich. Thats how it works with mine anyway when changing elevations.

The YZ cam timing mod is very worth while and really easy. The power will come on noticeably harder starting in the mid and you won't lose an ounce of bottom end torque. What a deal!

The manual recommends using fuel with a RESEARCH octane of 95 or higher. Most super unleaded pumps meet this requirement. Remember, the octane number on the pump is the research number plus the motor octane number divided by two.



Thump on!
Thump on!

 

[wayneo426]

Otay!

I agree w/ Buckwheat on the YZ timing. Best free mod, besides the wire.