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, suction after suction, raises and lowers the tapered needle, adjusting the mixture. When the diaphragm dries out, cracks, or develops holes, the engine stutters upon acceleration, lacks power on inclines, idles poorly, or starts with difficulty when cold. It is the part that fixes a carburetor that seems ready for the trash, and it fits the entire family of Leader 125-250 engines of the group: Piaggio, Vespa, Gilera, Aprilia, and Scarabeo.

✓ Strengths

• Original Piaggio spare part – code CM140301: the compound and elasticity of the diaphragm are exactly as designed, not an equivalent
• Avoids buying 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 to be replaced, even at low mileage
• Very broad compatibility – four brands and over fifty versions, from 2003 to 2016
• Available in stock, immediate shipping

Technical specifications

Compatibility

Who it is perfect for

This is the spare part for those who have a scooter that stutters when opening the throttle, lacks power on inclines, idles poorly, or struggles to start when cold, and has already ruled out the spark plug and air filter. These are the classic symptoms of a cracked or punctured carburetor diaphragm: the slide no longer rises progressively and the carburation becomes irregular. It is 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 been ridden for many kilometers.

Frequently asked questions

What part is this exactly?
It is the diaphragm piston of the carburetor, also called a slide or vacuum valve: the small piston with the rubber diaphragm that controls the tapered needle.

How do I know it needs to be replaced?
The scooter stutters during acceleration, lacks power on inclines, idles poorly, or starts with difficulty when cold. When 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 change the entire carburetor?
Almost never. If the carburetor body is intact, replacing the diaphragm solves the issue for a fraction of the price.

Does it fit my scooter?
It covers Piaggio, Vespa, Gilera, Aprilia, and Scarabeo 125-250 carburetor engines. Check the table and, when in doubt, send us your chassis number.

Is it original?
Yes: original Piaggio spare part, code CM140301. There are third-party equivalents available for less, but the diaphragm compound is not the same.