There are a lot of tiny fuel and air passageways in the carburetor that must be kept clean it order for your scooter to run right. Carefully, take the carburetor apart. This can be relative easy (on a 50cc scooter
). The carb has tiny passages that can get gummed up. Your scooter will not run correctly if the carburetor isn't completely clean, so take your time. I use a gallon container of carb dip (you can get a gallon at your local auto supply store).
First, remove all of the rubber and gaskets or they will get damaged. After a 20 minute soaking in carb dip, I blow out the carb with compressed air. You have to get all the jets and the passageways clean. Be sure the jets are clear, especially the starter jet. Sometimes carb cleaner won't clear out these tiny jets. Use a guitar or a piano string, a strand of copper electrical wire, or a tiny drill bit pin vise. Be sure not to increase the size of the hole in the starter jet or you'll change the tuning. Carefully reassemble everything, checking for cracks in the rubber carb boots and the gaskets. Replace them if they are old and cracked. Be sure and remove all rubber and gasket material first or they could get ruined. Spray carb cleaner also works if you're diligent.
If you have an electric choke, check it to make sure it works. Check the resistance between the wires - you should see around 10 ohms or less. Measure the length of the choke assembly. Remove the choke from the carb and plug the wires into a 12V source for 15 minutes. The choke body should be warm. Measure the length again - it should increase by around 1/8".
Next, consider whether your exhaust pipe is clogged. This is especially a problem with older two stroke scooters. The unburned fuel/oil mixture builds up in the exhaust pipe along with carbon over time. If the exhaust pipe is clogged, your scooter will run terribly or not at all. It can be difficult to tell if the exhaust pipe is clogged. The easiest way to tell is to remove it and try starting your scooter. It will be a bit loud - two strokes will sound like a chain saw. If it runs with the exhaust pipe off, you know that is the problem
hope this helps