<HTML>I have amoped and what I have done to it is put a smaller rear tire, smaller front sprocket, bigger back sprocket, and have gutted out the exhaust. All of these things will slow down the moped at top speed.
Gutting the exhaust will add performance all around but sometimes you ay have to change the jetting in your carb. this will be the cheapest thing you can do to your moped for better performance.
I would go with a smaller front sprocket. they are MUCH cheaper and easier to install.
I know what I am doing, Mine can pull wheelies for over a 1/4 mile by doing the things I have told you to do. I also added those foldable pedals you see on huge street bikes near the rear wheel on the frame. this make it easier to wheelies.