Piaggio CM140301 Carburetor Diaphragm Piston – Beverly, X8, X9, X Evo, Runner, Vespa GT 125-250

The Piaggio CM140301 is the carburetor diaphragm piston, an original Piaggio spare part. It is the vacuum slide assembly: the piston with the rubber diaphragm that, with each intake, raises and lowers the taper needle, regulating the mixture. When the diaphragm dries out, cracks, or punctures, the engine jerks during acceleration, lacks power uphill, idles poorly, or struggles to start when cold. This part can fix a carburetor that seems ready for the bin, and it fits all models in the 125-250 Leader engine family from the group: Piaggio, Vespa, Gilera, Aprilia, and Scarabeo.

✓ Strengths

• Original Piaggio spare part – code CM140301: the diaphragm's compound and elasticity match the original design, not an equivalent.
• Avoids a new carburetor – in most cases, this is the faulty part, and it costs a fraction of the complete assembly.
• Wear part – rubber ages on its own: on a ten or fifteen-year-old vehicle, it almost always needs replacement, even with low mileage.
• Very broad compatibility – four brands and over fifty versions, from 2003 to 2016.
• In stock, immediate shipping.

Technical features

Compatibility

Recommended products

• Carburetor gasket kit – to be replaced every time the assembly is opened.
• Jets, taper needle, and float needle valve – the other parts that age along with the diaphragm.
• Air filter – a clogged filter shows the same symptoms as a damaged diaphragm: replace them together to be safe.

Who it's perfect for

This is the spare part for those with a scooter that jerks when accelerating, lacks power uphill, idles poorly, or struggles to start when cold, and they have already ruled out the spark plug and filter. These are classic symptoms of a cracked or punctured carburetor diaphragm: the slide no longer rises progressively, and the carburetion is off. It's also the first part to check on a vehicle that has been sitting for a long time: the rubber dries out on its own, even without having accumulated mileage.

Frequently asked questions

What exactly is this part?
It is the carburetor diaphragm piston, also known as the vacuum slide or valve: the piston with the rubber diaphragm that controls the taper needle.

How do I know it needs to be replaced?
The scooter jerks during acceleration, lacks power uphill, idles poorly, or struggles to start when cold. Upon disassembling the carburetor, the diaphragm appears hardened, cracked, or punctured – often the hole is only visible when held up to the light.

Do I need to replace the entire carburetor?
Almost never. If the carburetor body is intact, replacing the diaphragm will solve the problem at a fraction of the price.

Will it fit my scooter?
It covers Piaggio, Vespa, Gilera, Aprilia, and Scarabeo models with 125-250 carbureted engines. Check the table and, if in doubt, send us the VIN number.

Is it original?
Yes: original Piaggio spare part, code CM140301. Aftermarket equivalents are available for less, but the diaphragm's compound is not the same.