Rejetting you scooter can be performed at home as long as you understand how to access the jets in the carburettor. Having the right tools will prevent damage to the scooter, and understanding how a combustion engine works also helps. Once rejetted, the scooter will run better and be more fuel efficient.
Locate the carburettor on your scooter. Open up the carburettor box with a screwdriver if the carburettor has one. Remove the air hose attached to the carburettor intake. Put any parts in a plastic bin nearby so you don't lose them. Use a socket wrench with the appropriate socket and screwdriver if needed to release the carburettor from the engine. Disconnect the throttle cable from the carburettor if possible.
Place the carburettor on a worktable or clear space with light. Use a screwdriver to release the jet assemblies from the carburettor. You may need to open up parts of the carburettor to access them. Wash out the jet assemblies with carb cleaner. Dry them off with a shop rag.
Remove the main jet from the jet assembly if it is attached. Use needle-nose pliers to handle the jets, but make sure not to scratch them. Locate the needle if the jets on your carburettor use needle jets instead. Write down or note the number of the jet to be removed. Use a larger replacement jet to increase the flow of fuel to the engine. Use a smaller jet to reduce fuel flowing to the engine. Repeat the process for your idle, mid-range, and top-range carburettor jets.
Reassemble the carburettor with the new jets. Make sure to clean out the carburettor with carb cleaner and dry it. Replace the old carburettor gaskets exposed with new ones. Reconnect the throttle cable. Take the reassembled carburettor and reattach it to the engine with a socket wrench or screwdriver. Reattach the air hose. Tighten all necessary clamps as needed. If applicable, close up the carburettor box over the carburettor.
Test drive the scooter. After a few minutes, pull over and remove the spark plug with a socket wrench. Look at the colour and determine if it is brown, white, or oily black. Redo the jetting process if the spark plug is white, using a bigger jet to add fuel. Use a smaller jet if the spark plug turns out to be oily black on the tip, reducing the fuel flow. Repeat the process of rebuild and testing until the spark plug tip shows a chocolate brown colour when riding.
- When buying a larger or smaller jet, make sure to buy extra ones of different sizes. They aren't expensive, and having a variety gives you the ability to make adjustments tuning your scooter carburettor.
- Perform each step carefully. Carburettors are usually made of aluminium, which can be stripped or bent easily by metal tools.