Re: 80cc bike really slow
A lean condition, caused by a bad intake seal, will cause a loss of power and bogging.
You need to read the spark plug to get a good idea of why it's so slow. Chalky white or no color means it's too lean. Wet or black means it's too rich. Brown means a good mixture.
Search for "plug chop". It's the process by which people tune carbureted engines (at least those that don't use a wide band O2 sensor). The process has been around for years, so there's a plethora of knowledge on the subject.
Replace the head nuts with shoulder nuts
Check the head nut torque
Replace the spark plug boot (you can find a good one at sickbikeparts.com)
Change the spark plug to an NGK b5hs (auto parts store)