Tuning with Fuel Screw (and/or Needle?)

Ok, I read up here often, I've searched high and low, but I have faith in the WR brain trust to put some comprehensive answers to how to use your fuel screw in one place.

First, my problem - as it gets warmer up in MN, I tend to get the problem of the motor killing at smaller throttle openings off idle. Happened on my '98, now on my '07. My understanding is this is why I installed an adjustable fuel screw. But, I could be entirely off and should be dropping my needle a notch?

What does the screw actually do? Does turning it in lean or richen the mixture? I've never understood if it's actually controlling fuel or air.

Last, what would be the probs/symptoms of having it too far in or out?

As it is, I set it at 1.5 out when I installed it, and I think I've turned about .25 in when it starting warming up around here.

Thanks in advance!

You're getting a rich bog off idle. As it warms up you need to lean your jetting out. The fuel screw controls fuel flow in the lower throttle positions so turning it in ( clockwise ) leans the bottom end.

Once you start using it you will find yourself fiddling with it alot as temps and altitudes change. It can make some amazing differences.

You really should read the sticky in the jetting forum. I know with our temp differences here in Canada the fuel screw is not enough, I have to lean my pilot and main out in the summer.

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