Best upgrade for the money! I bought this expansion chamber Last friday (10/4/18) and it arrived in a week. Excellent customer service and package tracking. This expansion chamber fit right on my bike (Only had to hammer a slight dent for the tip of my petal to clear it Use a cloth when doing this to avoid scratching the chrome). Over all provided my cheap costway 66cc engine with 5 extra mph, and gives the motor overall great throttle response and dont even get me started on the added torque+acceleration. Best $50 I could've spent on an upgrade. 10/10 would recommend, and i'll be getting another one when I buy my next motor kit. Also, it made my bike loud, so be cautious with your local law enforcement. I live in an area where the cops dont care, but generally the louder and faster you're bike, the more attention you draw. Sounds equivalent to a 2 stroke dirt bike. If you care, you can polish off the rough welds, but it looks better rough in my opinion.
The Expansion Chamber enhances a 2-stroke engine's power output by expanding the volumetric efficiency. It also provides a boost in the top end speed as well as improving the use of the left over energy from the burnt exhaust exiting the cylinder. This helps aid the filling of the cylinder for the next cycle.