Hi, morning, my '72 R75/5 is suddenly experiencing an inconsistent idle after running great...

Carbs were rebuilt by Phill Cheney at MAX several years ago, I adjusted valves last season (all okay) and I just upgraded to new coils, plugs and plug wires and it was idling consistently and evenly - the past two days, not so much. It DOES run great at speed, fyi. And it will idle ok when warm, then 5-10 seconds after stopping - slowly slow down where I have to goose the throttle to keep it going, then it will be fine...but at times not hold a decent idle...bad gas? I put some dry gas in tank...no difference. Thoughts?

Thanks for reading, Chuck