Did you buy a 50cc engine and install an 80cc bbk? Which bbk?
I did. It's a Chinese engine, and hi-tech Chinese kits are almost always high-quality. The machining is flawless, and the kit parts are all interchangeable for any given bore size, no matter which company made the kit. There's several different types of heads: 2-valve, 3-valve, etc. And the kits with included cylinder head work cost a little more, but work better than using your stock head. Your stock head will work, but the compression ratio will be higher than ideal. You can buy a race cam from any maker, and it will fit any other maker's engine, so just pick one. Order an extra set of matching gaskets (about $10) to be safe. To get higher speed with your higher horsepower, you have to change the rear gear set. Any gear set will do, just ask for a ratio that's 10% faster than stock. Or 20%, whatever you like. Increase jet sizes 1 or 2 sizes. Don't change anything else to start with, no rollers, weights, whatever. Leave the rest alone, including the carburetor. Takes about a day to swap everything over. After it's running (not before), you can try swapping the CDI ignition for an unrestricted unit. About $20.
