High Idle @ Times - Yamaha YFZ450 Forum : YFZ450, YFZ450R, YFZ450X Forums
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post #1 of 7 (permalink) Old 01-27-2008, 08:05 PM Thread Starter
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My 2005 YFZ will start and idle fine (thank goodness, it's been almost 18 months and a lot of $$$ to get it back together). It'll idle fine till I revv it up a little, then it gets stuck at high idle. We thought that it was the slide sticking, so we took the carb off of the air box and the cylinder, and tried to get the slide stuck by pumping the throttle. The slide wouldn't get stuck anywhere, moved smooth as butter. I took the top cap off of the carb anyway and doused it with carb cleaner while working the throttle back and fourth.

I put everything back together, and it still idles high as soon as I give it some throttle, if I leave it alone, it's fine till I stop again, then it idles high. The only way to get it to not idle high like that is to put it in gear, and let the clutch out slowly, then pull it back in after it starts to roll a little bit. Then it idles low like it should, till I go for a ride and stop, or revv the motor a little bit.

My friend that was helping me turned the black spoked screw on the back of the carb when we were trying to get the thing started. I'm wondering if that isn't my problem. Should I get it started, let it idle high, and mess with that mixture screw till the idle kicks back down?

Blue 2005 YFZ 450
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post #2 of 7 (permalink) Old 01-27-2008, 08:19 PM
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thats funny, cuz my 06 does the exact same thing...can someone shed some light on this, its kinda annoying...

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post #3 of 7 (permalink) Old 01-27-2008, 08:36 PM
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A friend had the same problem. We checked everything from the throttle cable to making sure the carb slide wasn't sticking....no problems. Guessing I adjusted her idle (the black spoked knob your friend adjusted on yours) and the problem went away. I turned it in and then turned it back out...hasn't done it since.

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post #4 of 7 (permalink) Old 01-27-2008, 08:45 PM
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Black knob is the idle. In (clockwise) is higher rpm, and out (counterclockwise) in lower rpm. YFZs do come with a pretty low idle stock so if u remember how it was keep it a little higher than that.
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post #5 of 7 (permalink) Old 01-28-2008, 02:48 AM
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Sometimes bumping up the pilot jet a size will cure this.


2006 YFZ478 - Cylinder Works Gen3 98mm cylinder, Venom pump gas 98mm piston, HR 63.4mm crank, stock cams (modded), FCI Intake, Jardine RT-4, Ricky Stator
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post #6 of 7 (permalink) Old 01-28-2008, 05:52 PM
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if you doused it in carb cleaner pull it back apart and check to see if the rubber gasket in there is messed. A buddy of mine just did that to mine and it ruined that little gasket. Its 7 bucks to get a new one...
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post #7 of 7 (permalink) Old 01-28-2008, 07:04 PM
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Someone correct me if I'm wrong, but I took a carb to a buddy to get cleaned. He had a bucket of stuff, no clue what it was called, but he told me I had to take it completely apart, because it would eat all the rubber gaskets and stuff in it. Just a thought for when you use some carb cleaner.

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