Wr450 wont start

15 replies to this topic
  • topp38

Posted August 25, 2014 - 11:18 AM


Hi all..got some moto wheels for tge bike...fitted tgem took it out to see how they were..i got a few hundred yards and tge bike died..it wont fire up since..it sounds as tho its going to start but thats as far as it goes.cleaned carb..good spark..all checks done twice over..its not fuel as i put petrol down the barrel and it still wouldnt start..so i think it must be electrical? I noticed exhaust valves are out of spec.0.15 is fine but tge spec of 0.20-0.25 is wey to tight...wid this stop it from starting.or should i go down the electrics side of tgings..and if so what should i check

  • Krannie McKranface

Posted August 25, 2014 - 01:29 PM






gotta shim you valves and do a leak down test

  • topp38

Posted August 26, 2014 - 09:22 AM


Its getting fuel...nice blue spark..and it has plenty compresion when kicking it over

  • Krannie McKranface

Posted August 26, 2014 - 03:15 PM


Its getting fuel...nice blue spark..and it has plenty compresion when kicking it over


There is no way to tell how good your compression is by kicking it over

Your auto decompression at kicking speed reduces comression to 50ftlbs so it will start easily

Once running it's up near 140ftlbs


Have you pulled the float bowl yet to see if there is debris in the pilot?

  • dirt-thrower4

Posted August 26, 2014 - 03:18 PM


Check carb and if all else fails it's probably your valves..more often than not, the pilot jet gets stopped up.

  • topp38

Posted August 27, 2014 - 09:41 PM


Thanks for tge reply...Pulled the carb apart.blew out all jets with airline..carb is spotless...air fuel is set..when i try n start it.it just just pops..but doesnt fire...ive read u cant do a compression test couse of the auto decompresion

  • dirt-thrower4

Posted August 27, 2014 - 09:45 PM


Try tuning the fuel screw. It sounds like it is not getting enough gas..

  • topp38

Posted August 28, 2014 - 09:26 AM


I have mate..it was set at 2 and a half turns out..jets havent bin change...but i have adjusted it a few times either way..but still the same...juat pops when trying to fire up....its got me stumped..ive tryed all the usual stuff 4 times over...driving me crazy

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  • dirt-thrower4

Posted August 28, 2014 - 09:29 AM


It must be valves then....you said they were out of spec yes?

  • topp38

Posted August 28, 2014 - 09:38 AM


Ye mate just tge exhaust ones..but tgere not properl close..i can get 0.10 in the way it should feel...but would tgat make tge bike just die? As if i hit tge kill switch?
Closed i meant mate..lol

  • Krannie McKranface

Posted August 28, 2014 - 02:49 PM


Valve adjust ment has to be spot on to the specs

  • ThumpMe

Posted August 30, 2014 - 04:47 PM


 First sign of hard starting usually means the valves need adjustment....BUT since you said it died suddenly  I would take out the little center cap on the left case and  see if the bolt that holds the flywheel tight is loose. It is a simple quick check and has been known to happen before. The factory even sent out a bunch in '03 that all did this.Mine even did it a few years later.


 What year is it? 

Edited by ThumpMe, August 30, 2014 - 04:50 PM.

  • revelc

Posted August 30, 2014 - 05:57 PM


Sometimes ignition coils can fail causing symptoms like that. They can still spark but not fire enough to run. I'd start with the valves though. Then go from there.

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  • dirt-thrower4

Posted September 01, 2014 - 09:22 PM


I had the same case with my coil on my yz250f. That's worth checking out too...

  • DunmireD001

Posted September 13, 2014 - 02:28 AM


Stator's going out.

  • topp38

Posted September 28, 2014 - 05:11 AM


Checked.cdi..coil.and stator..all checks out fine


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