This system slows down the power at the engine before it goes to the chain.
This gearbox comes in a short and long type, this is the longer version with more distance between drive sprocket and clutch bell centre.
If changing from the short gearbox you will need a longer chain, if changing to this gearbox from the short version you will need to remove some chain links.
Mini Motor 47cc 49cc Dirt Bike Fully Auto Gearbox Clutch Dirtbike Minimoto