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rdefonce

Why is my YZ400F is idling too high?

8 posts in this topic

I just removed the carb, cleaned parts, and re-assembled.

All settings were as before carb removal. Throttle has play, I tried to fully back-off the idle adjustment. Got any ideas, thanks!

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I'd have to guess it's idling at 3000 rpm, and no the hot-start is not sticking out. (Choke's not out either.)

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Cracked/spliced hotstart hose, dryrotted carb boot, loose carb clamps, and possibly loss of the small little oring on the fuel screw can all play a role in that.

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Cracked/spliced hotstart hose, dryrotted carb boot, loose carb clamps, and possibly loss of the small little oring on the fuel screw can all play a role in that.

Jimbob69, thanks for tips. My old YZ has led a charmed life since new: climate controlled garage, low hours for a '99. (And this is how it repays me! I know, it's probably something I did but it's easy to pass the buck ain't it.) All the rubber parts are like new still, clamps tight, didn't mess with fuel screw. I will triple-check those things again though.

It's a really even high-idle; seems as though the slide is being physically held open. (Doesn't have a lean/uneven sound to it.) Could the needle be touching the main jet somehow? or possibly the metal-plate thing on the slide not be on just right and interfering somewhere?

I will have to dig in.

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Make sure your rebound throttle cable isn't freighed and hanging up inside the cable guide just up from the carb.

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Throttle cable was just a tad frayed, so I replaced that.

I discovered the problem: I installed the plate that "nests" in the slide upside down. :ride:

It's really easy to do; it even looks correctly installed when it's upside down. MY BAD!

Getting the slide out is somewhat of a puzzle, so now I'm getting better at it . . . should be good to go now, and thanks for all your tips. :thumbsup:

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