trouble shooting help please (YZ450F)

4 replies to this topic
  • leon0183

Posted July 29, 2009 - 08:25 PM


Looking for some advice on what may be wrong:
Bike: 2005 YZ450F
Problem: Bike will start fine when cold and idle fine for about 30 seconds, then it will die. Only way to keep it running is to turn up idle or keep throttle open. After it is warm it is hard to start and i need to give it gas while kicking it. If i try riding it sputters and cuts out.

It all started after I accidentally left the drain tube catch plug in (used for super moto) and it filled up completely, backing up to the carb and keeping it from running. after i noticed that unplugged it, it ran fine for the rest of the race. Got it home and it started with the problem above.

What I have tried:
Carb: thought something may have got in carb. completely removed and cleaned with carb cleaner and compressed air. did not help.
New gas: did not help
It seems electrical (unrelated to the drain tube catch) so i tried:
New spark plug: did not help
Test Throttle position sensor: within spec for resistance
Spark test: seems weak
kill switch: continuity good
Spark plug cap (ignition coil test in manual): out of spec at .2 omhs range is recommended at .08 - .1

Do you think the cap could be bad? would this create the problem above? does it make sense that it would work fine until the engine warms up? could it be valves?

Any help would be great.

  • ben_suhard

Posted July 29, 2009 - 08:30 PM


A couple things to check, if you haven't already, considering you've already cleaned it, would be that the fuel screw still has it's o-ring and that the hot-start plunger isn't letting air in(if it's hanging open).

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  • leon0183

Posted August 04, 2009 - 06:43 PM


thank you. ended up adjusting the fuel screw. seems to run fine now. taking it to the track tomorrow, we will see if it keep running well.

  • MikeyT750

Posted August 05, 2009 - 04:51 PM


Ha, Ha. Simple things sometimes. I remember I thought my motor wascomming apart. Turns ot it was just my newly installed skid plate vibrating. LOL. Glad you got it.

  • ben_suhard

Posted August 06, 2009 - 12:12 AM


thank you. ended up adjusting the fuel screw. seems to run fine now. taking it to the track tomorrow, we will see if it keep running well.

Good to hear.:thumbsup:

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