Bonneville America Forums Forums Technical Forums Performance Mods Harley idle mixture screws

Has anyone had mixed results when using the knurled after market mixture screws. I installed a set this spring and had poor fuel mileage and erratic idle all summer. I repeatedly checked for vacuum leaks and carb sync but could not seem to find the problem until today. When the screws were installed I set them at my previous settings about 3.25 turns on one side and 3 turns on the other and assumed all would be well, I was wrong. Today before riding I thought I would try and adjust the screws for highest idle speed, highest speed was achieved when the screws were bottomed out. Backed the screws out 2 turns and went for a 150 mile ride. Decel remained the same( no popping), No performance change that I could detect (maybe even a little crisper) and a dramatic increase in fuel mileage. If anyone else has had a this happen to them I would be very interested in your comments.

LKR,

Have you done any other mods? I have done quite a few, including the knurled pilot screws, and they haven't given me any problems.
My bike had the erratic idle (not to be confused with Eric Idle) since new. I corrected it by removing the 2 vacuum port covers on the front of the intake manifolds and installing the AI flexible hose between those ports.



This seems to help modulate the idle....

BTW, not my idea, someone else on here came up with it....

Do you remember what the ends of the HD screws looked like? If they tapered to a point, the adjustment will be really touchy. The stock idle jet is shaped to take a really blunt needle valve.

Let's see if this works....



This picture is from the site where I bought mine. Not the clearest pic, but they look like the ends are rather sharp to me.

Grump, Are you running the crossover on both the manifold and carb vacuum ports?
Mike

Mike,

You can use either. As you can see in the picture, I chose the ones on the manifold. It was a better fit for the length of the AI line.

Hey LKR
Are you positive that you didn't lose the o-ring and/or washer that sits on top of the spring? When I pulled my screws one side came out, but the other (right side) o-ring and washer stayed up inside the screw hole -- for a few seconds. Then they dropped out and bounced off the engine case. Luckily I saw them fall. It took me several minutes fo locate them on the concrete floor. I don't know how it would run without them but I imagine it would be bad.

Just a thought.
Cody