I guess it could be a plug, but make sure your ignition battery is charged and your low speed circuit should be adjusted to be as lean as it can be and still have it respond quickly when the throttle is opened on a warm engine.

I adjust my low end in a little at a time until when I open the throttle quickly it dies, then I back off enough to correct that. This will make the engine so that you must allow it to warm up before you can open the throttle, if it's any richer thahn that it's too rick on low end.

TF