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Yamaha YFZ450 will not run with out choke

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I have a 04 YFZ, with a TBR exhaust, Hot Cams intake and exhaust cams, K&N air filter and supposedly a high compression piston. The bike ran ok when i got it. rode the bike around and wasnt happy with the throttle response, bogged down too much. I figured the fuel mixture was off, so i installed a longer fuel mixture screw. I rode the bike around, getting it in top gear and almost full throttle, pulled the clutch and the bike shut off, then i could not keep the bike running. it would start with the choke out, but as soon as you pushed the choke in it would immediately die. i could start the bike with the choke out and take off and push the choke in and the bike ran great, grab the clutch and it would die. i would also get a couple abnormally loud pops on deceleration. i dont have any experience with carbs, i have read a lot of forums but they have not resolved my problem.

i have read some forums saying that the TORS system may need to be reset, but i never found directions on how to do it.

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sounds like you have a clogged pilot jet.you should remove carb and take off the bottom bowl and clean all jets.the pilot jet is the one that screws out with flat blade screw drive.it will have 4 tiny holes on side and a honeycomb type hole inside. spay carb cleaner in it.hold up to a lite to look inside.good luck

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I have replaced the Piolet screw as well as the needle jet and main jet. I assume There are different size Piolet jets could I have too small of a piolet jet? Assuming that pulling the choke makes a richer environment increasing the diameter of my pilot jet would give more fuel. During 0-15% throttle, correct?

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Not sure what you mean by "installed a longer fuel mixture screw" as I do not have a YFZ450. How many turns out is your air screw? Set it at 1 1/2 turns out from lightly seated position.

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When you made the change in exhaust / cams..did you change your jet sizes according to manufacturers recomendations?

If not, take it to a shop (or anyone with an Exhaust Gas Anylizer) EGA and have your air/fuel ratio measured.

My guess is that your jetting is waaay to lean, and running with the choke out is the only way your able to compensate for the lean mix.

CAUTION: an overly lean condition can lead to high heat and engine failure very quickly.

The EGA check, and rejet will generally run you between $45 to $75, depending on the shop.

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sounds like you have a clogged pilot jet.you should remove carb and take off the bottom bowl and clean all jets.the pilot jet is the one that screws out with flat blade screw drive.it will have 4 tiny holes on side and a honeycomb type hole inside. spay carb cleaner in it.hold up to a lite to look inside.good luck

Classic symptoms!!! Clean the carb...paying particular attention to the pilot jet.

And....I would spend the money to have it gone over by someone who really knows carbs. You messed with the idle screw, and who knows if it was ever properly jetted in the firt place......

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I have replaced the Piolet screw as well as the needle jet and main jet. I assume There are different size Piolet jets could I have too small of a piolet jet? Assuming that pulling the choke makes a richer environment increasing the diameter of my pilot jet would give more fuel. During 0-15% throttle, correct?

If pilot screw turns out more and that dosen't solve your problem then you bigger pilot jet that what cuases bogged and backfire when on and off gas

You don't need a EGA just look at Spark plug if it clean the runing to lean.

It During 0-25% throttle

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