I picked up a derelict bike for $50, looks like fun, right? The bike is a Dynacraft Magna, the motor I'm not sure what it is. It has a date of 2012 on the motor. Rusty, flat tires, broken, rusted cables. I cleaned it up, aired up the tires, put clean fuel and a new NGK B6HS plug, got it started! Fixed the cables, took it for a ride. After a bit, it would hit about 20MPH. Problem is, motor sounds rich, 4-stroking, all speeds, low power. Adding any choke makes it worse. So I bought a "racing carb", with 5 different jets, $25 on Amazon. Even with the smallest jet, 65, still rich, low power, black, wet plug. Checked muffler, not clogged, runs same with muffler cap off. Same as with air filter off. Seems to have fair compression. Any thoughts? Thanks!