I had my Holley 650 re-built by a pro shop. Installed and runs great! However, I can't adjust the choke. It does not have a choke cap, only a single wire, and I don't see any means for adjusting. Upon start up the choke plate is partially open and returns to full open on warm up. Older model Holley, ca. 2000

 

A Holley electric choke looks like this. I don't know what you mean by "does not have a choke cap". Post a photo of what you have, because I haven't seen a Holley electric choke with only one wire. Or are you talking about a cable for a mechanical choke?

 

Ok, here is a picture of the carb. As I recall from years ago, there should be a plastic choke cover that you can turn to adjust the butterfly.

 

Loosen the screws and rotate the plastic cover to adjust the choke. The one wire is power. The ground is through the carb body. Be sure that there is not a gasket between the choke coil and the choke housing.

 

Thanks Joe. That did it.