2008 YZ450F hard to start

10 replies to this topic
  • Larrybeck

Posted July 22, 2013 - 05:26 PM


Bike is hard to start valves are in spec. Did notice water level was a little low. I ride two to four time a week. Any help will be appricated!!

Larry Beck

  • Larrybeck

Posted July 24, 2013 - 11:07 AM


Did a compression test and it has 100 pounds of compression.

  • 123devinzz1

Posted July 24, 2013 - 04:21 PM


Did a compression test and it has 100 pounds of compression.

do a leakdown. compression test isnt really helpfull when you consider that the autodecompression is taking place when the engine isn't running.

  • grayracer513

Posted July 25, 2013 - 06:12 AM


That's true, but with 100 psi, compression isn't implicated as a starting problem. Valve timing shouldn't be, either, but you should check it nevertheless. With that good, and the ignition making spark, the thing that normally makes the bike harder to start that it ought to be is the carb, specifically the idle circuit adjustment.

  • mike_dean

Posted July 25, 2013 - 05:43 PM


I have an aftermarket fuel screw in mine and it was getting harder to start and stalled on me a few times, finally checked the fuel screw and it had vibrated out to 3.5 turns was normally 1.5 turns, turned it back in and all was good, I now check it often.

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  • Larrybeck

Posted July 27, 2013 - 06:18 PM


Fuel screw was out 3 turns and the plug was black. Everything else seems to checkout we will see tomorrow.
Thanks for the help hope it works out!
Larry Beck

  • Larrybeck

Posted July 28, 2013 - 04:12 PM


Ok rode today and it was still hard to start and when I get hard on the throttle from idle it bogs really bad. I'M SO LOST PLEASE HELP!!!!

  • rangerclass7sx

Posted July 28, 2013 - 04:21 PM


if its too lean its hard to start

  • jdgunnoe

Posted July 28, 2013 - 05:23 PM


Your way to lean in the pilot circuit. Check the stickys in the jetting and intake section on how to dial your pilot jet and idle in. A bog is normal, if it does it while you are riding is when there is a problem. If this happens you are running the wrong size leak jet. I fixed this with the boyesen quickshot 3 ap cover. Had same problem of my ktm 250 f and this was the issue

  • Larrybeck

Posted August 02, 2013 - 04:57 PM


Well checked valves again they were good counted pins between dots and it was 12 reset it to 13 and reset timing and starts first or second kick! Still has a deceleration light popping tho but it starts! Thank You everyone for the help and the older post on this helped a lot.  What should I look at for the popping?

  • NitrousR1

Posted August 07, 2013 - 04:13 PM


The Decel popping is completely normal. Every yz450 with the proper size pilot jet will do it. Some people over compensate with a larger pilot jet to lessen the popping but now your too rich.

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