CDI units

7 replies to this topic
  • wr-426

Posted July 27, 2011 - 09:51 PM


my new to me 2001 WR 426 is having troubles. it runs fine when trundling down the road with the throttle just cracked but it won't idle and the with throttle anywhere between 1/4 and 3/4 it pops splutters and make very little power. the way the bike runs is very dependent on throttle position. if i ride the bike really hard and just open it up it runs the way it should and i have to keep my eye on the front wheel to make sure its not up in the air.

I have been through the carby very thoroughly at least three times and i know carbs fairly well so unless there is something particularly obscure that i could have missed i can't see there being any other issues with the carby. the plug is black and sooty every time i check it but no amount of leaning the mixture is stopping my problems.

I got hold of a CDI unit from an 03 WR450 which i could try but i am wondering if it compatible. i can't afford fry this CDI. I also have a the carb from the 450 which i could try but yhis would requite quite a bit of fiddling to make it work.

Does this sound to you like an ignition problem and can i try the other CDI? or if it doesn't where should i go next.

P.S valve clearances are within spec and everything's fine under the tappet cover.

  • wr-426

Posted July 28, 2011 - 12:24 AM


Well i managed to chase up a CDI from a 2001 WR250, plugged that in and i still have the same problem. i have only had this bike for about two weeks and the first time i rode it, it ran fine. now it runs terribly. it is really starting to frustrate me, any suggestions or ideas would be greatly appreciated.

  • dgcars

Posted July 28, 2011 - 01:47 AM


Well here we go....
1. Idle. Sounds like a blocked pilot jet and/or passage.
2. Have you tried it with the TPS unplugged?
3. Throttle plate installed correctly? No cracks?
4. Worn emulsion tube.

  • wr-426

Posted July 28, 2011 - 04:31 AM


thanks dgcars for your help. Your suggestions sound like good ones. it's definitely not the idle jet, i have check and made sure it is clear many times so i am quite sure of that. i did try it with the TPS unplugged and it kinda ran differently but not really any better. i don't think it would be that something has worn out as i had it running fine and things suddenly went bad. by throttle plate are you talking about that thin metal plate that sits on one side of the slide? is there a way that i could have installed it incorrectly.

I am now sure that it is a carby problem because i put a carb from an 03 450 in it and my problems have disappeared. i am thinking about ordering a full rebuild kit for the FCR and replacing all the
o-rings seals and gaskets and seeing if that sorts it out.

does anyone know a way that i can test the TPS? i have heard that it is difficult to reset them on to the throttle shaft. if anyone can shed some light on this it would be much appreciated.

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  • dgcars

Posted July 28, 2011 - 06:07 AM


You could have put the plate in upside down. Easy to do, trust me I know. Square end goes down.

  • William1

Posted July 28, 2011 - 09:59 AM


If dg's suggesstions do not resolve it, my money is on a bad stator or coil. Does it get worse as the bike heats up?

  • wr-426

Posted July 30, 2011 - 10:28 PM


hey guys,

the bike is running great with my friends carby in it. now i just need to figure out what is up with my carb so i can give his back. i am checked and cleaned pretty much everything in there very thoroughly and the only thing i am wondering about is could it be the TPS causing my troubles. is there a way i can test my TPS, and how easy is it to swap them. i hear there is some tricky aligning to be done when replacing them.


  • dgcars

Posted July 31, 2011 - 12:39 AM


The best advice I can give you on that one is to arm yourself with a multi-meter and a manual. I don't have any experience with the 426.
However, with the TPS disconnected the bike should revert back to a base or an RPM map. In this mode, it should run OK, but with less power.


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