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What is the best leak jet size

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I have an 05 wr250f as well I'm at about 6000 feet and went with a 55. the bike come stock with a 95. after i completed all the mods i felt would give me the most bang for the buck( Grey wire, air box, baffle) I had a real bad bog when blipping the throttle. I changed the leak jet and bought a zip-ty fuel screw and the bike pulls the front end up no problem in 1st 2nd and 3rd. the 55 should be fine for your bike but it wouldn't hurt to get a couple of larger and smaller to experiment. they are only a few bucks a piece. it takes about 5 minutes to change. loosen up the rubber boots pull the throttle cable out and rotate the carb. you can now easily pull the float bowl off and change the jet. like I said invest in the zip-ty as well. this will help you make fine adjustments. with my leak jet and running my fuel screw a little rich the bog is gone completely. it will give you a lot more confidence when setting up to clear obstacles.

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Did you measure your AP squirt duration before changing out the leak jet or just experiment with different leak jet sizes?

I've got a #70 leak jet in there right now and the bog is driving me batty. I haven't measured the AP squirt duration yet.

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I checked out the duration on mine but did not time it. What i did was move it a quarter turn in each direction while blipping the throttle and it just got worse. the factory set up was good for mine. You still need to go down in size on your leak jet. The carb needs to compensate for the vacuum loss with additional fuel. I would start out with at least a 55 leak jet and go from there. Remember the larger the jet the less fuel goes to the carb and more is directed back to the float bowl. The smaller the jet the more fuel hits the carb. :cry::cry:

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It could be 40, 50, or 60 or whatever. EVERY BIKE IS DIFFERENT. You have to put a little effort into trying different sizes to find what works best for you.

Good luck,

Obie #723

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Testing different settings seems to be the key. I've already experimented with different needle clip positions, fuel screw settings and main jets and it runs great at all throttle positions ... it just doesn't transition well (bog).

I ordered a #40, #50 and #60 leak jet last night from North Texas Yamaha (prices were considerably lower than PartsFish). They should be here by the end of next week.

jason

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