I have a motorized bike with a stock engine. Found a bike online with a big ass exhaust, Reed valve, the red speed card, and it's ported. I switched out the body part(the middle section with the ports) between the two bikes so now the stock one is on the bike I bought. It still has the speed carb on it and a windowed piston, but now has stock exhuaust. I don't know why, but when I give it throttle, it like won't do anything. It idles fine and the throttle works then, but when the clutch is out I like don't really go anywhere. Like it sounds bubly or something. It worked completely fine before I switched the body Btw. Any ideas of the problem?