Tuning a scooter can provide a noticeable boost in power if performed correctly, and it can be done inexpensively. To tune a scooter, you need to understand the relationship between sufficient fuel flow, air intake, and how a combustion scooter engine works. In doing so, then you can tweak the three-part formula to increase power output and efficiency from your scooter. The difference can be a peppy two-wheeled vehicle versus a sluggish mode of transport.
Use a socket wrench to loosen the stock exhaust pipe connected to the scooter engine cylinder exhaust stub. Use a larger socket and the wrench to loosen the stud holding the pipe to the engine frame next.
Take a small piece of wood and position it on the downpipe of the exhaust. Smack the other end of the wood piece with a hammer to free the exhaust. Remove the old exhaust. Purchase a performance exhaust that fits your scooter engine. Position the new pipe under engine.
Connect the downpipe of the performance exhaust to the cylinder. Bump it up into the cylinder with a rubber mallet. Secure the main exhaust bracket to the engine frame with a stud and socket wrench. Either connect downpipe spring hooks or tighten the cylinder stub clamp on the pipe to hold it to the cylinder.
Disconnect the ignition cap on the spark plug in the engine cylinder. Use your socket wrench to loosen and remove the stock spark plug. Replace it with a new one that runs at least one grade colder, which is needed for a hotter performance exhaust. Tighten the new spark plug with the socket wrench. Replace the ignition cap.
Use a screwdriver to disconnect the carburettor from the intake pipe or hose. Unscrew the bottom of the carburettor with a crescent wrench. Remove the current stock main jet with a flathead screwdriver. Replace it with a larger main jet per the performance exhaust manufacturer's recommendation. Close up the carburettor, tighten the bottom with the crescent wrench and reconnect it to the intake hose.
Start the scooter engine and let it idle. Confirm the scooter engine can run in park with no issues. Take the scooter for a ride and bring extra jets and spark plugs with you. After 20 minutes pull over and turn it off.
Use a socket wrench to loosen and remove the spark plug. Look at the colour of the plug tip. Put the plug back in if the colour is brown. Change the main jet to a bigger one if the colour is chalky white. Use a hotter spark plug if it is oily black.
It's always better to foul spark plugs running with too much fuel than not enough. Spark plugs are cheap and easy to replace. The opposite could cost you a cylinder and piston, which are much more expensive.
If you feel the scooter suddenly tugging when riding it at full throttle, you may be experience a soft seize, where the engine is running too hot without enough lubrication. Cut the engine immediately and coast in neutral until you can safely pull over and stop. Letting in run while seizing will eventually destroy the engine.