A CV carb like that, I'm assuming it's a Harley 40mm, has an enrichment circuit rather than a traditional "choke." Even on a Harley they were always a bit on the lean side, especially off the bottom and when cold. If the carb was pre jetted for you, you may want to find out what the pilot and main jets are and go up one size on the pilot. There are also several really good upgrade kits available for that carb via the motorcycle aftermarket, or even your local HD dealer. A good kit for that carb is a Dynojet kit, which comes with a new needle that's adjustable, softer more responsive slide spring, richer pilot jet and a tool ( a large metal screw and drill bit really ) to remove the idle air mixture plug installed at the factory to prevent tampering and meet EPA emissions, if it hasn't already been removed. If it has you can try richening the idle mixture by backing out the mixture screw 1/4 turn at a time. Hope this helps.