HELP !! 08 yz 450 f

9 replies to this topic
  • bill petitt

Posted February 15, 2009 - 07:40 PM


Got to the track. Bike started 2nd kick, as usual. took off on track. Hit the first jump. Felt like a bog on take off. Almost like something was blocking the exhaust pipe . 1/2 a lap, coasted in. Bike died. I changed plug. Plenty of fire. Tore down carb(3 times:bonk: ) Nothing. Bike wont start at all. I checked timing, by looking at the mark on the cam and it was TDC. ANY CLUE? Any where to start? What about the sensor for the carb? I am new to Yamaha and I am not sure if they have a notorious issue or not Any ideas before I start tearing it dow? Thanks

  • grayracer513

Posted February 15, 2009 - 10:44 PM


Do you have spark?

  • YZ KLX Rider

Posted February 15, 2009 - 11:32 PM


spark would be good to start with?
sounds to me like the valves

you either have a major or radical change in valve spec

tear the top off and check them

  • bill petitt

Posted February 16, 2009 - 08:12 AM


Spark is good

  • grayracer513

Posted February 16, 2009 - 08:40 AM


If the spark is good, and the timing and compression are good, then it's a fuel issue.

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  • rdefonce

Posted February 16, 2009 - 09:42 AM


Yeah, could be a fuel flow issue. Check your tank breather valve, could be malfunctioning

  • bill petitt

Posted February 16, 2009 - 09:55 AM


Checked the fuel breather line and the gas cap(just in case). I would think if it was a valve issue, it would make some sort of noise, don't ya think? That dang honda would make a noise if the valves were out by .001!

I appreciate you guys taking the time to try to help me. If I ever get to the bottom of it, I will let you know.

Thank you again


  • urgreathero

Posted February 16, 2009 - 09:57 AM


check float level in carb
that'll make it bog and not start

  • urgreathero

Posted February 16, 2009 - 09:58 AM


also check ur jets one may be clocked with a small chunk of dirt that'll do it also

  • xr50er

Posted February 16, 2009 - 10:13 PM


is the gas on?

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