The membrane sits between the intake manifold and the cylinder, controlling the mixture intake through small valves. Piston down: valves open, mixture flows in. Piston up: valves close. If this doesn't work well anymore, you'll notice immediately. The scooter starts harder, accelerates less well, or the mixture leaks back after it has been sitting for a while. At Fresh Parts, you’ll find membranes for all kinds of different models.
Replace or upgrade
If you want to keep the scooter to factory specs, a standard membrane from Piaggio original or Polini is the logical choice. The metal plates fit directly back, no hassle. Replace the gasket immediately as well: it's off anyway, and a small leak costs you power right away. If you want more from your 2-stroke engine, carbon is the next step. Carbon valves respond faster, close tighter, and give your engine a more direct throttle response.
VL11, VL13 or VL16
The Malossi VL11 fits directly on a standard Piaggio 2-stroke engine block without modifying the crankcase. Handy if you want carbon without any milling. The VL13 is most commonly used in tuned setups from 50cc to 180cc, including the Gilera Runner 125 and 180. This is the largest membrane that fits without modifying the crankcase. The VL16 is specifically for race setups with larger engine capacity and a larger intake. That requires crankcase modifications.
When to replace
Hold the membrane plates up to the light. If light passes through or they no longer lie flat, they need replacement. Bent, blackened, or cracked means replace immediately. If the scooter floods after a few hours of standing or is hard to start in the morning, a leaking membrane may be the cause.
Ordering membranes at Fresh Parts
Order before 10 PM and your order will be shipped the same day. If you’re unsure which membrane fits your setup, please contact Fresh Parts customer service.
Frequently asked questions about 2-stroke scooter membranes
What does a membrane do in a 2-stroke scooter?
The membrane controls the intake of the air-fuel mixture via small valves that open when the piston goes down and close when it goes up. Without a properly working membrane, the crankcase doesn’t build pressure and the mixture doesn't enter the cylinder properly.
How do I know if my membrane is broken?
Hold the membrane plates to the light. If light shines through or they no longer lie flat against each other, they are worn. Other signs: the scooter is hard to start in the morning, floods after being stationary for a few hours, or has noticeably less pull than usual.
What is the difference between a standard and a carbon membrane?
Standard membrane valves are metal and are the direct replacement for the original. Carbon valves are lighter and stiffer, which means they open faster and close tighter. This gives a more direct throttle response and better cylinder supply, especially with a tuned setup.
Does a Malossi VL13 membrane fit my Piaggio without modifications?
Yes. The VL13 is larger than the original membrane but still fits inside the crankcase. If you want better throttle response but not that aggressively, the VL11 membrane is also an option.
Which scooters are compatible with the Malossi VL13 membrane?
The VL13 fits Piaggio and Gilera 2-stroke engines from 50cc up to 180cc. This includes the Piaggio Zip, NRG, Typhoon, Zip SP, and the Gilera Runner 125 and 180. All models with a Piaggio 2-stroke engine are eligible, and none of these require crankcase modifications.
Should I replace the gasket when changing the membrane?
Yes. When the membrane is off, the gasket is off too. A reused gasket won’t seal properly and can cause an air leak, which immediately leads to performance loss. Always order the gasket together with the new membrane.