That pump removes fuel vapor from VST and send it back into air box, only when float level drops in VST. It does not assist the VRO/OMS. If your not getting fuel to carbs check VRO output
Thems old top hat heads...if you took .015 off cc's only increased by maybe 2cc . Trash stablizer,set at 22° at WOT cranking and set idle where motor is happy close to 2°