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2002 WR 250 F Jetting?


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I just recently bought a 02 WR 250 F and the carb was really jacked up. The bike sat for 2 years. I took the carb apart, jets out, ultrasonic cleaned it, dumped and flushed tank and refilled with 91 pump gas.

Jets are such, 172 - 72 - 42.

Needle is set a 4th click.

Fuel needle is set at 2 turns. Plug looks good.

Mid and top end runs great. Idles ok.

When you blip it, the rev stays high for a sec or two before it drops back down?

I live in Norcal and generally ride at 3000' elevation.

What should the jetting be and what are these symptoms?

Yamaha refused to tell me what the jetting should be because they said that 02 carbs are all over the map.

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Well.... there is stock jetting as installed when new and then there is what people have run. But you supply insufficient info to tell if what you are running is theoretically close to being correct

Temps?

Any modifications - Airbox, exhaust, engine?

What needle code?

Now, being your complaint is about idle, that is easy enough for you to figure out with just the following hint:

Fuel Screw/Pilot Jet

Fuel screw settings in the 'book' are recommended starting points. Every bike is different, as is the temp and altitude. Set the screw according to this method. Do it with the bike fully heated up.

Gently turn the screw all the way in. Now back it out two turns. Start the bike and fully warm it up, go for a 10 minute ride. Set the idle to speed to 1,500~1,800 RPM as best you can (I know, without a tach this is tough, just set it to were it idles relatively smoothly). Once warmed, slow the idle to the lowest possible speed.

*** When turning the fuel screw, keep an accurate 'count' of the amount you are turning it and record it in case you have to reset it for some reason. Makes life easier when you can just set it from notes Vs. going through the procedure again.***

Turn the screw in until the idle becomes rough or the bike stalls.

if it stalled, open the screw about 1/4 more turn. Restart it and slowly screw it in till you can just perceive a change.

If the screw can be turned all the way in and the bike still idles perfectly and does not stall, then you need to go down a size in pilot jet.

Now very slowly, open the fuel screw till the idle is smooth. Blip the throttle, let the bike return to an idle, wait say ten seconds. Confirm it is the same smooth idle.

If the screw has to be opened more than 3 turns to get a smooth idle, you need to go up a size in pilot jet.

If you find it does not stall with the larger jet but has to be open more than three turns with the smaller pilot jet, put the larger one in and set the fuel screw at 1/2 turn.

If the idle speed increased, adjust the idle speed knob to return the bike to a real slow idle speed. You must then re-visit the fuel screw. Keep doing this till the fuel screw is opened just enough to provide a nice steady idle at the lowest possible RPM. Once this is done, increase the idle speed to the normal one for your bike, typically about 1,800 rpm, but go by the spec in your manual.

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I got my JD Jetting Kit today and followed the instructions.

Used the Blue needle at the 5th click, 185 main, and 2 turns out on the fuel.

Used the thicker o-ring on the pump timing screw for a snappier response.

Just follow the instructions. No Brainer.

0-4000' jetting at approx.. 85F.

Idles great too.

Shazam!!!! Imagine that!! Runs like a champ! Rips!

Edited by wrphreak
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