Rebuilt 03 yz 450 not starting

2 replies to this topic
  • kaminski347

Posted July 24, 2011 - 04:48 PM


I just rebuilt this 03 yz 450 after its been siting for a couple years. Ive been trying to start it but its not going well. I change the plug and getting spark. I believe Im getting fuel bc the I can smell it on the plug.

I kick it over a bunch and all I get is a few puffs of smoke and occasionally a backfire.

Could I possibly have the timing off? I timed it according to the manual but I was wondering if maybe I could have the timing off and have it firing on a decompression stroke instead of a compression stroke?

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  • Schpenxel

Posted July 25, 2011 - 12:10 PM


Has the fuel in it been sitting for a couple of years too?

If it's been sitting even for a few months (or it has sat at any point with fuel in it without being cleaned out) then the carb needs to be cleaned very well. Pilot jets clog very easily.. it's almost easier to just replace them so you know they're clean.

That sounds like your problem to me.

Also, your timing can't be "halfway" off. The plug fires every time the piston goes up, regardless of whether it's a power stroke or exhaust that is not your problem.

  • kaminski347

Posted July 25, 2011 - 03:37 PM


It is fresh gas and I did talk the carb and just sprayed carb cleaner through everything sometime in January but Ill look into replacing the pilot jet.

Thanks for the info on the timing.

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