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southerlin55

engine cut out problem

14 posts in this topic

I have a YZ450F that runs good when it is cold but once it warms up it has no power. i cant seem to figure it out. I changed the gets so there not cloged and its jetted for altitude.

any ideas?

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yea it runs fine when its cold but once it warms up it feels like a bike does when your trying to bump start it down a hill that isnt big enough like it wants to fire but it wont.

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you can make about four laps and it will run all the way through the power band, as soon as it gets warmed up it falls on its face from half throttle to full. southerlin55 posted this tryin to help me out but i finaly got logged in so i can go further into detail

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third clip and a 165 or a 162 not sure the pilot jet but i have been running this same set up on the same bike same area for three years and it just started a couple weeks ago

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the cap is good its hard to blow through but you can blow in it though

That doesn't sound quite right to me. I just went to the garage and checked my 426, and my vent check valve on the tank is very easy to blow through in one direction, and very hard in the other.

Is your's the same way? If it isn't working properly, or is installed backwards, it can contribute to fuel starvation.

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Air must be able to easily enter the tank. The checks in the vent line and gas cap are designed to allow this, while discouraging fuel from flowing out through the vent. Check to see if yours is working that way.

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if you blow on the hose it is difficultif you suck on the hose it is about the same way. would this make a diff if the engine was hot or cold?

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What happens is that the pressure in the tank is somewhat normal when you start out. As fuel is removed, the air pressure drops, causing air to enter to fill the depression. If the air enters more slowly than the vacuum is created, the vacuum will eventually get to a level where it stops the fuel from flowing to the carb.

The sure way to test for this is when the engine is acting up, stop and loosen the cap enough to break the seal. If the engine then runs normally, you have your culprit.

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