yzf wierd off idle

6 replies to this topic
  • barry

Posted July 27, 2002 - 03:46 PM


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

  • John_Lorenz

Posted July 27, 2002 - 03:50 PM


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.**** ]

  • barry

Posted July 27, 2002 - 03:57 PM


no i have not done this mod

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

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Mark_UK

Posted July 29, 2002 - 02:47 AM



reduce the squirt length to <.5second
did mine at the weekend,
feels fantastic now

  • Fly-nBri

Posted July 29, 2002 - 05:28 AM


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

  • Shawn_Mc

Posted July 29, 2002 - 07:01 AM


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.

  • xtreme165

Posted July 29, 2002 - 07:07 AM


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.

Related Content


Snake pit oct 30th by The Anvil

Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies

Is it worth it? (Cam and High compression piston) by macgi77

Dirt Bike   Make / Model Specific   Honda   CRF 150/230 F/L
  • Hot  36 replies
WR Camshaft Swap Info - last post by jamesm113

WR Camshaft Swap Info

  • 0 replies

Megabomb Fitment by 288yz450

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 1 reply

BIGBORE FOR YZ450F 2006? by Taattie94

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.