Put Air Cleaner on, cart starts but will not rev up

[BrewCityMusic]

Getting a little tired of how finicky this thing is, new Coil, Plug, carb, etc - ran great for a couple of days now suddenly it won't rev up with the air cleaner on, even if I pull the element (filter) out of the box. I popped on a simple cone and it runs OK again, tried the original box and back to the same issue. The tube from the carb to box is slightly collapsed, so I tried putting a piece of tubing in there to hold it open but that didn't help - what the heck am I missing here?

[Bryce]

Double check your air intake manifold (part that connects the carb to the engine). Maybe connecting the air box is putting stress on the manifold and opening up a crack or causing a leak somewhere.