Help?! trouble starting 450f

7 replies to this topic
  • IamRooster151

Posted December 17, 2010 - 07:38 AM


hello i have an 06 yz450f and it wont start. i dont know what it is if it is just the cold weather (20 degrees daily) or because i havent started it in about 6 weeks. tell me what i could do to get it started in this cold weather please. thanks alot

  • pembell

Posted December 17, 2010 - 10:26 AM


What have you tried? Changed the plug? Does it almost start, or just 'nothing'?

  • IamRooster151

Posted December 17, 2010 - 01:33 PM


just nothing i was thinking it might be a foul plug, or the cold weather but my 250f starts right up so i think it might be a foul plug

  • dgcars

Posted December 17, 2010 - 02:21 PM


Then take the plug out of the 2fiddy & put it in the 4fiddy....:excuseme:

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  • rmcr250r

Posted December 17, 2010 - 02:28 PM


If you put it away with gas then your gonna wanna clean your carb.

  • dgcars

Posted December 17, 2010 - 03:21 PM


If you put it away with gas then your gonna wanna clean your carb.

6 weeks at 20* isn't gonna hurt that carb.....:excuseme:

  • brentn

Posted December 17, 2010 - 04:46 PM


No it's not.

These bikes have accelerator pumps, when you twist the throttle literally a shot of fuel goes right into the intake when the valves are opened and into the combustion chamber.

I found for hard starting bikes that have this to twist the throttle at the same time that you kick it over.
Had a crf250r that would not start for the life of me, probably clogged pilot jet or something. After realizing that it shoots a stream of fuel for a twist of the throttle, I tried it while kicking and it fired right up.

  • broncomoto

Posted December 17, 2010 - 06:01 PM


just did a valve job on my 06 yz450f b/c it wouldnt start cold. turns out center intake valve had no clearance. replaced that valve, went down fro 185 to 180 shims on both exh valves, decarbonized and viola! only problem now is the front wheel wont stay on the ground. ps. for this layman, diy valve job took time, but wasn't that hard to do. spent about 300 on the piston, rings the one intake valve head and base and the shims. yes I would have rather loaded that 2011 in my truck, but now im glad i didnt.

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