Over heating loss of coolant, won't idle, difficult hot starting

5 replies to this topic
  • kenmin007

Posted October 08, 2014 - 05:31 PM


I was trail riding and the engine bogged and stalled. Difficult to start after, once started rode back to vehicle. Noticed loss of coolant in radiator. Since then difficult to start. Engine will not idle below 3500 RMP even in neutral. Engine running very hot when riding loosing coolant from over flow tube. Need some help. If anyone had similar issues I would like to know. Thanks in advance for your help.

  • grayracer513

Posted October 09, 2014 - 06:49 AM


Lean idle mixture kind of problem.  Check to see if it can be corrected with the idle screw.  If not, a dirty pilot jet, blocked passageways, air leaks in the intake, or tight intake valves may be the cause.

  • kenmin007

Posted October 09, 2014 - 03:14 PM


Thanks for your information. The bike is your YZ450F 2006 has FMF exhaust with Wisco 13.2 high compression piston. The jetting on the bike is 170 main with 48 pilot standard needle in 5th position. The idle screw is completely closed if I open the idle screw it is difficult to start. Let me know what you think.

Thanks again.

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  • Arizo

Posted October 11, 2014 - 12:26 PM


I had also the problem high idling and overheating. The seals from my carb where flat and hard. Maybe you also have a vacum leak

  • kenmin007

Posted October 12, 2014 - 04:31 PM


Took off carburetor today to clean it. When re assembling I noticed that the valve plate was upside down. There is a hole on the plate and I had it on the top. When I cleaned it last time I reassembled it wrong. Idles good now however when I went for a test drive it died and was difficult to start. I will check it tomorrow, starting to get frustrated. Just want to ride.

  • Arizo

Posted October 19, 2014 - 02:51 AM


I had the same with my previous carb. The plate was also upside down by the previous owner. Ok i can understand i had the same with my bike

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