Dies down. Boggs down after 25 mph. Power at first. Then nothing.

[Tgerde]

Ive taken the carb apart and cleaned the jets
 Nothing is clogged. Its pretty clean on the inside. It starts, idles no problem. Rides no problem for maybe a half a mile then as soon as I hit 20-25 it bogs down an the engine dies. I thought it could have been a faulty gas cap. Letting an air bubble in. That's not the case I've cleaned the carburetor with seafoam. And I am just beyond myself.  I would really appreciate any advice anyone has

[eamartin]

Which Super 8 is it, how many miles, how long have you had it, when did it last run correctly, does it have the factory air filter?