So very stuck...

Got it, that's what I was asking.
You're not talking screwing with the mechanical advance springs are You?!?! If so, no no no, leave that sh*t alone, You only need to adjust the screw in the can. The arm on the can controls the total the can add to the base & mechanical, if adjusting the diaphram spring tension to max is allowing light pinging or a slight surge, get a can with a lower advance arm.