Most scooters use some kind of a throttle cable activated at the handle to increase fuel flow to the scooter engine. The cable tightens when the throttle handle is pulled back, pulling on a carburettor slide. This action opens more fuel to the engine, making the assembly run at a higher speed, producing more power. However, cables are made of steel and eventually break. Replacing them involves installing a new cable.
Use a screwdriver to loosen and remove the screws that keep the scooter headset sealed. Open the headset top enough to be able to see inside and access the throttle handle. Locate the throttle cable connected to the handle rod. Identify the cable housing the cable inserts into to travel into the scooter body.
Open up either the scooter seat or scooter side panel by hand to access the carburettor. Locate the throttle cable and housing connecting to the top of the carburettor. Check to see if the old cable is already severed by tugging on it. Cut the old cable with cable snippers either at the carburettor or handle end. Grab the old cable sticking out of the housing and pull it completely out.
Throw the old cable away. Use a crescent wrench or screwdriver to open the top of the carburettor. Pull the top off to expose the throttle slide inside. Insert a new throttle cable end through the top opening from the inside out until the end with the lead stop on it is all that is left. Position the stop into the slide so that it hooks into the slide's cavity -- this feature allows the cable to pull the slide open for more fuel. Reattach the top back onto the carburettor body.
Take the free end of the carburettor and cover it with grease using your hand. Slather the entire cable except the very end. Insert the cable into the housing near the carburettor. Shove the cable into the housing until the other end eventually pokes out of the housing at the headset near the throttle handle. Line up the headset end with the pulley on the inside end of the throttle handle.
Attach a pinchbolt to the end of the cable in the headset once you pull it snug, removing any slack. Use a screwdriver to tighten the pinchbolt on the cable. Insert the cable and pinchbolt into the groove in the pulley on the throttle handle. Redo the process if it is not tight. Check that the pulley pulls the throttle cable correctly by pulling on the throttle handle once connected. Look at the carburettor and confirm the throttle slide is being pulled as well.
Reattach the scooter headset top and resecure it by screwing in the screws with a screwdriver. Turn the scooter on and test the throttle to confirm the engine responds correctly when the throttle is pulled for more fuel flow.
Most hardware stores have generic pinchbolts in stock. Ask a clerk to show you where they are in the speciality hardware section of the store.
Do not install the cable without first greasing it. Eventually the friction inside the housing will wear down the steel cable and it will snap, causing you to have to replace it again.