Just purchasted my Shadow and it seems to be only

Gas could be old, but it sounds more like you are losing spark to that cylinder at low rpm. Try a new spark plug, they're cheap. If that doesn't help, you could have a particle clogging the pilot jet of that carburetor. The pilot jet only works until you throttle it above idle. If it's clogged with a little junk, it will make bike idle terribly. Try spraying some carb cleaner through it (the one not running) with the engine on, and see if it likes the addition of fuel to that one cylinder. THis will tell you if you're lean on that jug. Good luck. Let me know. TT