I've been asked by a Forum member to comment on this subject. Yes, the Idle Mixture Thumbscrews I sell are also sold to fit H-D carbs. But H-D uses -a- Keihin CVH carb and Bonneville's use Keihin's CVK carbs. The major difference being that the CVH is intended for single carb applications and the CVK's are linked pairs.
Older non-CV Keihin carbs use a much bigger idle mixture screw, so if you are buying them from a H-D house, be sure to specify the newer CVH carbs.
Above the screws are a spring, washer and o-ring. The o-ring is extremely small and very easy not to notice if they fall out. I belive that this is the route-cause of any problems users are experiencing. I recommend placing a rag or dish under the carbs when you remove the stock screws.
It is also my opinion that if you need more than 3-1/2 turns-out to get your bike to idle correctly, your Pilot jet is too small. Under 1-1/2 turns... Pilot jet is too big. I have found that 2-1/2 turns-out (as the factory recommends) is an ideal starting point. At least, I base my jetting recommendation based on 2-1/2.
Now; before anyone goes Jihad on me, let me say that I am not presenting myself as the end-all of Bonneville experts. I base my opinions on what I personally experience with my own Bonneville's, as well as feedback from my customers including many dealers. There are many variables that go into optimum jetting and there is no such thing as one size fits all.
Michael Selman
SEL-MOTION
