You can make your four stroke scooter faster by installing a number of products or making one of a handful of aftermarket alterations. The alterations and products available have the potential to increase your average speed by one to three miles per hour each. If you choose to make all of the potential alterations available to you, they could improve your four stroke's top speed by five to ten miles per hour.
Alter the variator system by installing aftermarket variator pulleys. The exact process of installing aftermarket pulleys depends on the size and type of pulleys you purchase, but for any scooter it will require you to remove the faceplate of the variator case which is held on by six bolts. You will then remove each pulley wheel by unscrewing the centre bolt holding them in place. Use an impact wrench to do this.
Alter the variator system by removing the restricting washer underneath the front pulley wheel. Open up the variator system, remove the front pulley wheel and pull the washer off of the front pulley rod by hand.
Increase the air flow to the engine. This can be accomplished by either drilling holes into the air intake (located above the variator case) or by removing the intake altogether. You can drill or poke holes into the intake with any size drill bit or awl, as it is non-rigid plastic. Drill holes anywhere on outer wall of the intake. The intake is attached to the scooter by two or three bolts, usually with two attached to the underside of the rear wheel well and one attached to the variator case. Unscrew these bolts to remove the intake entirely.
Swap out your scooter's current muffler. Unscrew the fastening bolts located near the connect point between the exhaust pipe and the muffler. Pull the old muffler off of the exhaust system. The new muffler can be installed by reversing the order. The new muffler will enable your scooter's engine to expel exhaust faster and cleaner, allowing more air to enter the engine during fuel combustion.
Consult your owner's manual and a motorcycle or scooter mechanic or salesperson to determine what type of replacement muffler system you should purchase and install. Base your decision on your performance desires. For example, if you don't mind sacrificing quietness for speed, you might choose to leave the muffler off entirely, or you could install a lightly packed muffler. If you want a good balance of performance and sound muffling, you would likely pick a more thickly packed muffler. Replacement mufflers are universal depending on how large your scooter's engine is, not necessarily on the make and model of the scooter. For example, mufflers for 50cc scooters can be installed on any 50cc scooters. The exception to this rule are scooters that have developed proprietary parts (for example, Honda). Your manual will indicate the engine size, and the mechanic or salesperson will show you the range of muffler options.
Attach a windshield to the handlebars of your scooter. This will cut down on wind resistance. How you install the windshield depends on which windshield you choose, but usually it involves removing the aesthetic panelling on the front of the handlebars and attaching the shield to the bolt holes that once held that panelling in place.
Check your rear tyre's pressure with a tire gauge. Compare the pressure with the max cold PSI number written on the sidewall of the tire. Under inflated tires will slow your scooter down significantly.
In some states, 50cc scooters that can travel over 30mph must be registered as larger class motorcycles.