wr 400 that wont idle?

I have a 99 WR 400 that will not idle without the choke being pulled out. Any ideas? It seems to run ok, and the dealer that did the work says to just ride it that way. They spoke to someone at yamaha and they said if it runs good like that the ride it like that. They told me it shouldnt hurt anything. I am going to take it out for a ride this after noon and see how it does.

If you have any ideas why it does this please let me kow. Thanks.

Slow jet is too small, i.e. too lean. Lazy, stupid f'n dealer.

The other possibility is that the carb needs cleaned and the slow (air) jet has clogged holes from old/bad gas. Take it apart, clean and inspect as necessary. You did not mention what the bike has on it (aftermarket pipe, ect). I wouldn't go back to a mechanic that told you to ride it that way.

it does have an aftermarket pipe onit. I am not sure what kind, it was there when I bought it. I have tried to clean the carb. I will look into getting a bigger jet. Thanks. I should have it done by Saturday, I will let you know how it worked.

You don't say how long you've had it, but I found my mixture screw was turned all the way in and I had leaks from nearly every gasket on the carb.

You might want to take it off and check/clean the carb.


John, I think you've got the answer. I totally overlooked the fuel mixture screw. Backing the screw out has the same effect as enrichening the slow circuit. Brilliant!

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