'00yz426 low throttle misfire

4 replies to this topic
  • henrysdad

Posted July 11, 2004 - 05:50 PM


I just bought this bike a week ago.this is my street bike ,set up like supermoto. I searched the entire forum ,and found some useful info.Like the guy who has the same problem after installing the electrex wr ignition/lighting coil. I can't find that post(?!)again.I went thru the carb,It is all stock,as is the exhaust ,and the intake. It definately misfires at 1/8 throttle,any rpm,any gear. kind of random too,sometimes alot,sometimes not. it has an electrex light coil. I am begining to think this may be the problem. I tested everything the manual says to and everything is within spec. I hooked up my timing light to check idle rpm,and I watched the strobe,and at the throttle opening where this happens It is dropping spark. so now i feel it is electrical ,not jetting. I am getting confused. Has any one solved this problem?

  • Fastest1

Posted July 11, 2004 - 07:11 PM


I would suspect the CDI. The heat could be affecting it making it kind of random. Did you test it? Do you have one you could borrow from a friend? I probably have one in the garage if you need one. I run a wolf programmable so I really dont need the stock one. It is off of a 2000 also.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • henrysdad

Posted July 12, 2004 - 10:17 AM


I am thinking along those lines.I unplugged the tps today and the misfire almost is gone.And it started on the first kick,never was able to do that before .But it feels different,seems louder out the exhaust, and it backfires insanely on deacceleration.I have not tested the cdi ,that was the only thing I did not do..Unfortunately I do not know of anyone I can borrow from.If I come up with any funny readings ,I'll take that one from you.Thanks

  • henrysdad

Posted July 25, 2004 - 04:05 AM


I am still confused. I purchased a new CDI(not used/$26 ebay). that did not fix the problem.

If I unplug the TPS the misfire goes away.The TPS measures in spec, at the limits though.I cannot set it to the numbers in the manual ,it does not adjust enough.It is extra loud out the exhaust,when unplugged.

The lighting coil/stator are nowhere near spec for the stock magnito coils.

I talked to some racers at the local dirttrack event, all suggested richer pilot jet/different neddle. I will try that.still seems electrical to me. Any other thoughts?

  • bushy

Posted July 25, 2004 - 04:13 AM


Popping on decell is caused by a lean condition. 1/8 throttle is in the pilot jet range, so I guess they are right! :thumbsup:

Related Content


Is the 2016 GYTR Yamaha YZ450F too fast? by Fryboy

Dirt Bike   Special Interest Forums   Pro Racing
  • * - - - -
  • Hot  241 replies

Michigan Motocross Tires by 288yz450

Dirt Bike   Dirt Bike Regional Discussion   North
  • 1 reply

First Hare scramble tips by dhend8

Dirt Bike   General Dirt Bike Forums   General Dirt Bike Discussion
  • Hot  33 replies

YZ450F 03 Sparks driving me crazy by SirAttard

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies

100 hrs on 2014 yz450f, shim valves or replace them? by ttr230rider6

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  79 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.