2006 WR450F Odd problem with idle

When I bought my used '06 WR450F, it didn't want to idle. It wouldn't react to the fuel screw adjustments so I went up on the pilot. I ended up with a 52 which is quite rich for where I ride (sea level) if you compare to what everyone else is using (usually a 48). Bike was still hard to get warmed up and had a rough idle. One day, I noticed the idle improved. I ran it like this for two years.

Last month I removed the carb to install an adjustable leak jet and noticed that the tip of the fuel screw was gone!!! I had remembered that the screw had vibrated loose one day and was resting on the starter. That's probably when it broke off. (yes, the bike did stall). This was the aluminum aftermarket thumb screw. All I had was the oem brass so I put that in. Bike did not want to idle. Sounded very lean. Leak jet was set at #40. Obviously it was working fine with the broken off nipple on the fuel screw so I grinded that off the oem part, put it in and the problem was solved.

This makes we wonder though why my bike is so lean on idle to need a fuel screw setting and pilot jet so rich.

I wonder if I should up on the pilot again to where I can get a new fuel screw to work? I suspect a 54 or 56 pilot might be necessary. That is abnormal for a WR down here.


Either be willing to fix your bike properly or sell it. Doing 'repairs' like you are is just wrong.

Get the tip of the old screw removed from the carb. Have a pro do it. Get a brass or stainless extended fuel screw. Put in a 45 pilot. Adjust the fuel screw for a good idle.



Either be willing to fix your bike properly or sell it. Doing 'repairs' like you are is just wrong.

Get the tip of the old screw removed from the carb. Have a pro do it. Get a brass or stainless extended fuel screw. Put in a 45 pilot. Adjust the fuel screw for a good idle.

William, let me clarify. What I did was not a permanent repair. I should not have said "problem solved". I should have said "problem identified". I just discovered this issue 2 weeks ago and haven't ridden since. The purpose behind grinding the tip off was to diagnose the issue via the process of elimination. I wanted to see if the problem was the fuel screw or the newly installed adjustable leak jet.

The tip is not in the carb. This is a very tiny piece of tapered aluminum. It could only have fallen to the ground after breaking off.

Please let me restate the question. Could there be something else wrong with my carb OTHER THAN A PILOT JET? Or is it not uncommon for some WR450's to require greater than a 52 pilot jet at sea level?

Edited by Navaho6

Never would be the leak jet. Entirely different carb circuit and does not operate at all at idle (or anytime the throttle is not being opened).

You removed the carb from the bike,. removed the float bowl and are positive the tip is not stuck up inside the brass seat? That is common with the alloy fuel screw failures.

Assuming the tip is not jammed in the seat, that the float height is correct, that the needle jet emulsion tube is not worn out, that the slide is not worn out, that the release plate is intact (and not upside down) as well as the seal and that the slow air jet is installed and the passage ways are clear all that would remain would be having a idle speed too high and having the carb running off of the needle.

Thanks for the help but I think the best thing for me is to send it off to Zip-Ty Racing and have them go through it and check everything out. Might as well have them do their magic to it. I think it is $125 plus any worn out parts.

Sometimes, that is money well spent. Several TTers have atttempted to 'fix' a carb, having not enough knowledge and skill, only to have it turn into a nightmare.

Strike up a good line of communication with ZT and get a good explanation of what was wrong, how they discovered it. Stash the knowledge away. In time, yoo will have the touch to to it yourself.

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