Easy midrange flatspot fix

4 replies to this topic
  • Ga426owner

Posted June 06, 2001 - 05:45 AM


Like the rest of you, I aspire to things that make my bikes run better: On the WR426/250. There is a flat spot after 1/2 to 3/4 throddle. To fix this w/o all the rejetting discussion that fills this site up, try this simple fix.
Under the gas tank there is a black connector with 2 wires going into it. 1-solid grey/1-black & grey.
Disconnect the solid grey wire, seal up connections with Elect.tape or silicon. This wire is for a rev limitor that Yamaha has,to pass emissions. The other wire is the kill button. This should clean up a lot of the trouble owners are having with flatspots, jetting fixes that have no effect, etc....
This fix came from a source that spends a lot of time testing/racing for big blue. Hope this helps......

  • mcarp

Posted June 06, 2001 - 06:09 AM


Sounds great, but there's no way I'm personally unhooking the rev limiter. As fast as this beast spins to redline, I'll overrev it the first ride. The factory has big $$$ to spend, we all don't.

Also, I don't seem to have a flatspot. With YZ timing and good jetting, it revs so darn fast the midrange only lasts 1/2 second!

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  • wrooster

Posted June 06, 2001 - 12:17 PM



help me understand something -- how does toying with the rev limiter change the behaviour of the engine in the midrange (which by definition is below the engine's rev limit, some would say it's around 1/2 of the rev limit)?

the wrooster
'01 wr250f

  • Russ_P

Posted June 06, 2001 - 03:35 PM


I'm with mcarp, I would leave it alone. Get stupid, overrev the motor and float a valve just once and after having to dump at least a grand into a wasted motor you'll sit there and cry "oh why was I so stupid?!" I personally don't feel this illusive flat spot either though. Just my .02 worth :)

'00 WR 400

[This message has been edited by Russ P (edited 06-06-2001).]

  • Ga426owner

Posted June 07, 2001 - 04:16 AM


Russ P there is a chance on the 1998/1999/2000 WR400 that this may not be a issue. We are still working on this....

This fix is working on 2001WR250s from the WR/YZ250 post under "Whats wrong with the WRs"
Has anyone attempted to remove/disconnect the grey wire on a 2001 WR426 yet?????What results have been found??????.
I believe that this should clean up a lot of problems people are having with "Patchy Midrange issues", that jetting does not cure.
Also, there is a reason the non-US spec WR's don't have this issue --- they do not have the emission restrictions we do. That is why this grey wire is only applicable for US spec bikes. I do not think that any damage will occur - by disconnecting this wire. Why?
Because the non-US spec bikes do not have this & they are not floating Valves or blowing up.....


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