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new2blue450

idle prob..yz450

12 posts in this topic

okay YZ gods, got a question(again). i went out for a ride today and after about 2-1/2 hours when i let off the throttle, it would go down in rpms, but not back down to idle. (idled very high). if i put it in gear and let the clutch out enough to slow the engine, then let off it would idle normally. is wrong?? thanks guys.

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Have you adjusted the fuel screw for the colder temps? A lean condition (I believe) could cause a hanging idle....

Where's Gray when you need him? :applause:

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sounds lean to me...

If you're sure you have the right size jets in there, give the carb a good cleaning out.

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You might have gotten some goop in the pilot jet or other small orifice. Give it a good cleaning; carb cleaner and compressed air.

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Check the carb boots to ensure a tight fit. Make sure the hot start isn't sticking, as well. Other than that, it might be dirty inside like said before....how old is the fuel?

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it may be the hot start sticking, out of all the options that sounds the most likely...

I thought that at first too, but when he said that it happened after a few hours of riding that pretty much makes that not the cause.

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Just go back from riding and was about to post the same thing...after a few hours mine was idling high too...after a little bit it would idle back down.

Wondering if it isn't something to do with colder weather..Just richened up the carb..well the main jet anyway...pulled the plug tonight and it is showing perfect..barely any brown...checked my valve clearances and they are all in there....? I did mess with my fuel screw yesterday but why would it only do this after it has been run for awhile?

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Falling temps will cause lean idle mixtures, so if you're in that sort of weather, that's where you should start. Back the idle screw out a little, the problem may go away. If not, round up the usual suspects for other causes of lean idle (air leaks, etc.,), but don't get too carried away chasing lean mixture ghosts until after you've checked for tight intake valves. They're a common cause of "hanging" idle in the smaller YZF's, so it's worth a look.

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Sounds good.......i guess i'll back out my screw a little because i checked my valves today and they were all in spec....plus last week when i got the bike back together from rebuilding it that is one thing i did was go through the carb so i was pretty sure there wasn't anything in the carb.

However the gas i had was only about two weeks old...would bad gas be a culprit...seems to me like bad gas would just make it run bad throughout throttle range, not just idle...but i don't know.

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well, i messed with my idle and fuel screw.....it stopped for about 45-60 seconds, then started again......HELP!!!!!

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