RPM's hangin?

5 replies to this topic
  • shiftngo

Posted September 26, 2010 - 08:53 PM


Got a '04 YZ450F. Runs awesome but sometime the RPM's will hang like I'm choking it. I don't believe it's the throttle cause I twist it forward to make sure when it does it. The only way I've found to make it stop is (if I'm sitting) put it in gear and move it a little or (if I'm rolling) tap the kill switch just a little to make the engine stutter. But it only does it every now and again. Anyone got any ideas?

  • grayracer513

Posted September 27, 2010 - 05:40 AM


The idle mix is lean. It has tight valves, an air leak, a varnished pilot jet, or just needs an adjustment.


Posted October 05, 2010 - 07:29 PM


I have then this on a few bikes - on two it was the hot start having dirt in the plunger and hanging in the up position. Remove and clean the plunger and remember it has to seal the hot-start passage.

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  • MARQUEZ_697

Posted October 11, 2010 - 04:58 PM


i was having the same issue wit my 06 that im new on.... was thinkin it was jus the bike overheating (goin through some tight trail sections).... it didnt hang wen the bike was cooler and i checked for air leaks. hmm ill have to check the other things you guys metioned. oh and i just got done adjusting the valves on mine before this last ride. even checked them after riding to make sure they were still in clearence. will have to check pilot jet and mess wit my idle mixture...

  • dalonar

Posted October 11, 2010 - 06:55 PM


my money is on the hot start stuck on....just had this happen to me a couple days ago

  • jratcliffe3

Posted October 12, 2010 - 01:41 PM


Gray is right, its a sign of it running lean. Being as it's intermittent, I wouldn't count out a small piece of dirt or film being sucked into the pilot jet and dropping back out when you semi-stall the engine. Can't hurt to give it a good clean out.

Only other thing I can think of is a sticking floats in the carb - if thats sticking low it could affect the pilot circuit pick up slightly.

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