yzf wierd off idle

just a question

if i snap my throttle back quickly on my yz 400F i dont have an instant response

it blurps and almost stalls then it will rev up after that

its like once i snap the throttle theres a 3 second delay {sometimes almost stalls} before theres a response.

??? maby carb or jetting problems im thinking but am not sure what to do about it ??? any help is appreciated

Have you done any of the mods AKA BKmod or jetted the bike?

The Bog you describe is a known issue on the 426's I am not sure on the 400 though, I think they run a diff carb.

You might want to do a search on bkmod there are plenty of posts

to look at the mod you can get it a motomans site


[ July 27, 2002: Message edited by: E.G.O.**** ]

no i have not done this mod

would it clear up the problem and give me that instant throttle response ?


reduce the squirt length to <.5second

did mine at the weekend,

feels fantastic now

The BK mod doesn't refer to 400 f's. :)

There is a mod for the accel. pump on the earlier carbs. You basically just make a small limiter for the pump rod.

If this is a new malady Id clean the carb first. The low speed passages on this carb are extremely small. It doesnt take a lot to block one.

If you have to much filter oil on your filter this will cause it as well. Try riding your bike with no filter oil and see if it still does it. Dont go out and ride all day or in dust with no filter oil just do a test run but oil lightly when riding when I had a 400 this was what I found that to much oil on filter and it ran like grap off idle.

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