[1QuickS]

Same thing happened to me, fuel tank strainer filled with tank debris starved the engine. Let it rest awhile and AOK.

Disconnect fuel supply at one of your carbs and let the fuel pump run and check fuel delivery. This could be a dynamic issue in that the debris may fall away when at rest but while driving it is drawn into the filter and plugs it. The tank filter is a fine wire mesh or strainer so this "dynamic" could occur which would make your problem seem to be intermittant.