Leak jet help

[ohsobad_chevy]

We have a YFZ 450 with a k&n air filter (no air box lid) and a sparks full system. The quad is jetted perfectly as far as the pilot, main and the needle are concerned.....but the quad sputters pretty bad when you stab the throttle off idle. We talked to some guys at a local shop and they told us that we could change the leak jet. I know what a leak jet is, but I have no idea what to change it too. Does anyone have any good information on changing your leak jet to get better throttle response? I would appreciate any help I can get. :)

[GPracer2500]

What's in there now? You want to go smaller.

[ohsobad_chevy]

I have no idea..??.. I will do some research and see if I can find out what size is in it now.

I thought the ole boy said I needed to go bigger, but I don't know. Does the AP make it too rich when you first stab the throttle? :confused:

[GPracer2500]

Leak jet sizes work opposite most other jets. A smaller leak jet will allow the AP to deliver more fuel. Leak jets "leak" fuel back into the float bowl that would otherwise go out the AP squirter. The most common reason that causes that off-idle "throttle stab" bog is a lean condition created by the AP not squirting enough fuel. This is especially the case with no air box lid.

What year do you have? I think the 04 came with a #70, the 05 a #50, and the 06 a #40. I'm not sure about the 07. A #35 is the smallest size there is. If you need more squirt than a #35 allows then the options get complicated.

For reference, the 06+ TRX450R comes stock with a #70 and the HRC spec calls for no airbox lid and a #55. Not saying that's exactly the kind of change a YFZ will need, but if you've got an 04 with a #70, somewhere around #50 or so should be in the ballpark.

[ohsobad_chevy]

It is a 07, I will try to find out what stock size is and play with it till it hits good.