Fine tune jetting help.



I purchased a jetting kit, leak jet kit and fuel screw from JD Jetting for my 2006 wr450. Mods to the Bike are Smog stuff removed, Full pro circuit exhaust, yz exhaust cam, and open top air box (small 4 cell battery relocated, top of the airbox is open like a YZ). I followed JD's instructions and used the 168 main, red needle on 5th clip, 42 pilot, thick o ring. Fuel screw is 2 full turns out and I think I’m running a 30 or 35 leak jet. . I’m In Sacramento but my typical riding areas are 3k-5k feet in the sierra foot hills and central Nevada.


I have zero off idle bog. Bike runs great with no Decel popping at 4K feet when its 60-70 degrees out. When it’s cold out 30-45 degrees it pops bad. I was at 7500 feet when it was that cold. I was thinking the pilot could be lean but I get a little black rich puff out the exhaust if I crack the throttle fast. Am I dealing with a lean pilot but a rich accelerator pump? 


and yes by open airbox I mean THIS open: 



Adjust your fuel screw for max idle

Drop the idle with the idle screw and repeat ( if needed)

Shut off engine

Turn the fuel screw all the way in (lightly)

Count the turns

1 or less means you pilot is too big

2 or more means it's too small


When you go up in elevation, you become richer, not leaner.

So any popping is from an un-adjusted fuel screw for the elevation, or, cold motor and exahust

I'll add... the airbox is opened up too much. Return it to the size opening that it would of had with just all snorkle parts removed. That is more than big enough. Too open causes a weaker vacuum signal in the carb and results in poor operation over 1/2 throttle.

The air box is open just like a yz 450. The side cut outs are still intact. How can it be open too much?

Also just using the stock set up up would be bad since I run I giant look bag a lot and it covers up the grab handles where the stock holes get air.

William's point is that the lack of air pressure control at the intake bell of the carb will mean a vacuum null at  wide open throttle, resulting in less hp.

A YZ has a head that flows MUCH more fuel and air compared to a WR head, and a larger diameter exhaust header.

3 x 3" is all you need.

Well, if you factor in that the side cut outs on the 03-06 are still intact and my giant loop blocks the rear fender/ seat gap as well as the grab handles and part of the side there really is not that that much more air flow area that a bike with the baffle out and the side holes cut out. The bike pulls extremely well on the top end, better than my 05 did. I might try to block some of it to see if there is an improvement. 

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