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wedrivezs

'04 WR450 carb question - I'm baffled??!!??

4 posts in this topic

I bought my bike used, and with all the stuff done. My bro in law just bought an '05 and we're learning how to jet his bike.

Well, we decide to tear my carb down and see how it's jetted. Scott was having trouble getting the needle out, so he turned the throttle. Something happened and it was stuck WOT. My throttle stop had been cut WAAAAAY too short. Took us a while to figure out what happened, I couldn't explain it without looking at the book - but some black switch looking thing under the throttle cable cover had it's arm stuck in behind the throttle shaft making WOT.

Anywho, I was looking in the book and it says the throttle plate should be about 3mm off the bottom of the throttle bore. I noticed my carb maybe was at 1mm. So we adjusted it so a 3mm allen wrench was a little loose.

We got it all back together and it was revving up HUGE, felt like 1/4 - 1/3 throttle. So I started backing off the knob and it idled down.

Soooo, &%$#@! is going on? Why is it running with just a tiny crack of air to breathe?

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Yea, I hears of storys where the cut off throttle stop was too short and permitted overtravel and stuck at wide open. Wouldn't that be fun on a tight trail...

Diffinitely replace that stop screw.

The total length of (end to end) of the YZ stop is 0.975".

The WR stock stop shoild be 1.30"

I'm not sure I understand your problem now, It sounds like your idle is dialed down now. Could it have been wrong before the teardown?

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Anywho, I was looking in the book and it says the throttle plate should be about 3mm off the bottom of the throttle bore. I noticed my carb maybe was at 1mm. So we adjusted it so a 3mm allen wrench was a little loose.

We got it all back together and it was revving up HUGE, felt like 1/4 - 1/3 throttle. So I started backing off the knob and it idled down.

That 3mm adjustment is only for timing the AP. You definitely shouldn't have that gap at idle, and if so, explains the very high idle.
Soooo, &%$#@! is going on? Why is it running with just a tiny crack of air to breathe?
It runs with that "tiny crack of air" because it uses the air from the pilot circuit during idle.

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Ok, that solves it, I'm a BOOOOB! I must admit I was skimming the manual. I'll look and see what this "AP" is.....

Thanks fellas!

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