Cotten rebuilt an M-74b for me and I've just installed it on my '53 with a later model O-ring intake manifold. I followed the manual to a T on the low speed needle adjustment, made sure my throttle butterfly fully closes, and lit her up, but I can't get it to idle down as it should regardless of where my low speed adjustment is set. As soon as I adjust it the motor begins to cut out and I need to put my hand over the carb. to bring it back to life. This says lean to me, as do the plugs. The bike is tough to kick too.
I'm wondering if my timing is set too far advanced hence the difficulty in kicking and the lean issue, or if this sounds like more of an intake leak? I won't be able to tinker until Wednesday evening and would appreciate your input in the mean time. FYI- We timed the bike with the flywheel mark in the rear 1/4 of the window.