Producers of Automatic Scooter may deliver your models, due to laws existing in Germany, only on 50 Km/h throttled. Most Scooter would be able to achieve 70 Km/h with their Engine performance ( up to 5 HP ). The Manufacturers have various possibilities throttling the Scooter:

1. Inlet reduction
Here between Carburators and Crankshaft housings a Screen with smaller cross section is let in the Inlet Port. Then there is only a reduced quantity of Fuel / Oxygen Mixture available to the Engine.

2. Throttling of the Ignition Unit (Ignition Box)
The Ignition is interrupted before achieving the maximum Speed. The Ignition Box can be replaced by an unthrottled version ( CDI - Ignition e.g. of Malossi ).

3. Variomatik
In order to achieve the maximum Speed, the driving Belt should obtain the longest gearing that is possible. Doing this by squeezing together the Wheels, the Driving Belt is pressed outward (on a larger Radius) and thus modifies the total Gear Ratio. A Shim prevents that entire move together of the Wheels so that the gearing is reduced, or possible terminal Velocity cannot be achieved.

4. Throttling at the Exhaust
The Exhaust is throttled in two versions. Either the diameter of the Elbow Union is reduced (Metal Ring), or a resonance Pipe is welded at the Elbow Union. Both prevents the Engine by negative influence of the Exhaust Oscillations to achieve the maximum permissible Engine speed.

A listing of different Models and their specific throttling is given here

Further Information to the topic can be found on the following Pages:

Aprilia - Scooters

Rollerpower

Dragster 2000

Scooterzone

Tunescoot