Fuel Air Screw / Idle Adjustment

5 replies to this topic
  • sasarris83

Posted March 03, 2013 - 07:42 AM


hey guys i am a newbie to this site and to the wr450f i just bought. i just have a few questions about the way this thing is running. it seems to start hard maybe 8-12 kicks on choke popping on a few kicks then finally starting. when it warms up and choke taken off it idles rough and has a dead spot at 1/4 throttle. it looks to the fuel/air screw is 2 turns out and the idle adjustment is screwed all the way in (which doesnt seem right to me). if i back the idle adjustment out it will just stall. like i said i just bought the bike and havent spent much time on it yet but if anyone has a good place to start that would be awesome. also if it matters im in NY and its about 30-35 degrees here now. thanks for your help

  • MANIAC998

Posted March 03, 2013 - 08:41 AM


They are notoriously lean when they are stock during summer temps, so they are really bad during the winter! Fresh fuel, larger pilot jet, adjustable air/fuel screw, clean air filter and it will be better. I would also check your valve clearances to make sure none of them are too tight. If your not willing to check them during the winter, then you will never find the time to check them during the summer! What year bike? EFI or Carb?

Edited by MANIAC998, March 03, 2013 - 08:42 AM.

  • Krannie McKranface

Posted March 03, 2013 - 08:43 AM


There are several things you should do.


1. re-jet. The stock jetting is useless. JD jet kit or follow the forum FAQ at the top
2. uncork the exahaust so it will run correctly. Again, FAQ
3. PROPERLY adjust the fuel screw. You put the screw at 1 turn, then turn the idle screw till it barely idles. Then adjust the idle with the fuel screw. If it goes to high, drop it with the idle screw and repeat.
4. Test your accelerator pump for proper squirt. They nozzle clogs very easily. You have to lift up the subframe to see it work.

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  • sasarris83

Posted March 03, 2013 - 09:15 AM


It is an 06 carbed and also has an adjustable fuel screw on the bottom with numbers. It just seemed weird to me that the idle screw is all the way in and will only idle there. I want to try making those adjustments while its running but just won't stay running if I make any adjustments. A friend also suggested the JD kit which I will Definitly buy ASAP. I also can't see a throttle stop unless its behind the cover where the cables go into the carb.

  • Krannie McKranface

Posted March 03, 2013 - 11:04 AM


The throttle stop is behind the black throttle wheel cover.

It's possible your idle screw cable is binding. It happens.

It's also possible that someone 'spec'd' a pilot jet and fuel screw adjustment based on an excessive high idle.

Does the idle drop quickly when you blip the throttle?

  • sasarris83

Posted March 03, 2013 - 11:18 AM


You know I'll have to get back to you on that one but when I take the choke off it takes a whole to come down to idle... If that helps. But when I blip the throttle it boggs. After the Rpms get a little higher I can blip it without the bogg.


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