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High idle when warm


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I'm trying to sell my 05 YZ250F.

It has been sitting for a while, since I ride my 06 YZ250 almost exclusively. I last rode it in November. I Sta-Bil'd the gas before putting it away like I always do.

Started it up, and it was running fine, except for the fact that it idles high. Trying to debug that demon. It actually did it when someone came to look at it, which was (needless to say) very embarassing.

So far I've:

Drained the old gas, and dumped Sea Foam and new gas in the tank. (still idled high after that)

Cleaned the carb with carb cleaner (was better for a while, then got crapped up once it was warm)

Adjusted slack in the hot start cable at the handle bars (idles better with the hot start pulled, riddle me that one!)

Disconnected the hot start at the handle bars (idled the same)

I'm thinking maybe I need to replace the pilot?

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well, why not lower the idle and then have it run on choke till its warm?

Idle is already all the way out, and it's still doing that, unfortunately.

Yes, replace (do not clean) the pilot jet

I figured. I don't have the stock size (42) on hand, but I do have a 45 (slated for

my 250, but i can always get another one for that or run a 48 in that bike) so I will try that one tomorrow. The dealer said he would have to order any size I needed (I guess that's why all the dealers around here are FAILING).

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Idle is already all the way out, and it's still doing that, unfortunately.

I figured. I don't have the stock size (42) on hand, but I do have a 45 (slated for

my 250, but i can always get another one for that or run a 48 in that bike) so I will try that one tomorrow. The dealer said he would have to order any size I needed (I guess that's why all the dealers around here are FAILING).

The Yamaha/Honda dealer here is the same. Luckily the Suzuki/Kawasaki dealer carries Keihin carburetor jets. Whatever size you want. Check around. 👍

Just because it's a zook or a kawi don't mean the Keihin supplied carbs don't use the same jets.

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i've never had to actually replace one...im not sure of the manufacturer but they sell a wire set that fits down the hole of the jet and helps to clean out any debris that wont come out with just carb cleaner and compressed air...but if its easier to just replace it put a new one in it

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Could you explain why replacing the pilot jet and not cleaning it is the right thing to do?

The openings in it are very small, and they clog easily. You could probably get it clean with enough work but it's a $3 part and it's just easier to replace it.

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Could you explain why replacing the pilot jet and not cleaning it is the right thing to do?

The orifice is very small and even a very thin layer of varnish or other type of build up can reduce the size enough to effect its performance. If it is clogged with a single piece of debris you can normally clean it out but it is impossible to completely polish the orifice to the exact size it should be when it has a layer of crud built up. Believe it or not some jets are so precise that even the texture of the orifice walls can effect its performance, think about that next time you are ramming a wire through one cleaning it out.👍

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  • 2 months later...

( 01 yzf250) I am new to the site as of today and found this article that seesm to be the same issue I have. I have cleaned the carb,replaced the pilot,replaced leaking carb o-rings (intake leak), and recleaned carb. The issue still persists, till last night when I warmed up th ebike and during the high idle issue I unplugged the TPS and instantly the idle went to normal. I did this a few times and each time the bike would return to normal. I checked today and the TPS sensor is quite expensive! Is their a test (ohm's) to prove it's failed or to adjust to? The previous owner had this thing all out of whack!

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