B75 V-Twin idling problem

[Ken's Honda]

I have a B75 that has been sitting for a few years in the garage of the previous owner. I took it home and it started on the second pull - he said he hadn't run it in several years. It starts with it choked and when I close the choke it dies - runs best at 1/2 choke. Once running it wont stay running with the choke comletely open or closed. However..... if I put it in gear and start it, it runs great and smooth and endless without the choke at low-mid to high RPMs. There is a jetscrew on the side of the carb that I have adjusted, however there is absolutely no effect on the engine rpm or performance - it even runs the same if I remove it completely. I am not a engine mechanic by any means, so any help for this old tar would be greatly appreciated.
Ken