Tuning on our 03 Z400 tonight. Got the main jet and needle where I want, but when you let off the throtte it pops a lot (in gear coasting down). Doesn't this indicate a lean pilot jet?

Also, the gas valve only works on "prime" like usual. I took it apart and it was clean and the little diaphragm was okay. With the valve in the "on" position, it starves out of gas. From the valve there are two leads--one goes to the carb and the other one appears to just sit there in open space. Is this a atmospheric pressure eqalizer or is it supposed to be plugged into something?

Oh also where's the air screw on this carb, under it or something? Never paid any attention and from the outside I don't see it.

Thanks in advance to you experts out there!

 

dont know much about the stock carb but I do know the fuel petcock uses vacuum to open it
sounds like to me that maybe the vacuum port is plugged a little. I just had my carb gone through
if was not performing like it was suppose to. was the bike sitting all winter? if it has I would pull the carb and have it cleaned
if you need a stock carb I still have it

 

Popping on decel indicates you are lean yes. I had the same prob, only did it in lower half of rpms, and i raised the needle and it went away.

From the vavle on your gas tank there should be one hose that runs to the carb for fuel and then another hose, the one closer to back of the quad, that runs to the carb also. It just pushes a gold stem and has nothing holding it on. Its jsut a vacuum line i believe and it sounds like yours is off. this might be why it doesnt run on ON becuase of no vacuum.