Polini CP carburetor guide for Puch mopeds

Estimated read time: 16 min read | Originally published: 11 June 2026 | Latest update: 12 June 2026

Polini CP carburetor explained: which size do you need for your Puch?

A Polini CP carburetor is a compact, performance-focused carburetor for tuned Puch mopeds. It controls the fuel and air mixture your engine needs to start, idle, accelerate and pull cleanly at full throttle. The correct CP size depends on your cylinder, exhaust, intake manifold, air filter and how you want the engine to behave.

At Puchshop, we sell several Polini CP versions: Polini CP EVO spigot carburetors in 19mm, 21mm and 24mm, Polini CP clamp carburetors in 15mm, 17.5mm, 19mm and 21mm, Polini CP spigot carburetors in 17.5mm, 19mm and 21mm, a 21mm clamp cable choke version with air filter set, a 21mm spigot version with air filter, and a 17.5mm replica spigot option.

Quick answer: Choose a smaller Polini CP if you want strong throttle response, easier street tuning and good low-to-mid rpm behavior. Choose a larger Polini CP if your engine has the cylinder, exhaust, intake and rpm range to use the extra airflow. Bigger is not always better: the carburetor has to match the full engine setup.

What is a Polini CP carburetor?

The Polini CP is a needle-type carburetor designed for small engines, scooters, mopeds and racing applications. Like other performance carburetors, it mixes petrol with air before that mixture enters the engine through the intake manifold.

The CP uses several tuning parts to control the mixture at different throttle positions: the float and float needle, idle jet, air screw, throttle slide, conical needle, atomizer, nozzle bush, air brake jet, main jet and choke or starter circuit.

The Polini CP is especially interesting for Puch tuning because it is compact, available in useful sizes and gives more tuning control than a very basic original-style carburetor.

Important: Always tune a two-stroke carburetor from a safe, slightly rich setup toward the correct setting. A mixture that is too lean can overheat the engine and cause serious piston or cylinder damage.

Which Polini CP carburetors does Puchshop sell?

Puchshop stocks the Polini CP range in the sizes most useful for Puch mopeds, from smaller street setups to stronger sport and racing setups. Use the product overview below to compare clamp, spigot, EVO spigot, air filter set and replica options.

Polini CP EVO spigot carburetor for Puch

Polini CP EVO spigot carburetors

Polini CP clamp carburetors

Polini CP spigot carburetors

Polini CP carburetor with air filter set for Puch

Polini CP carburetor sets

Polini CP EVO manual choke spigot carburetors

Size	Product	Mounting style	Best use	Shop
19mm	Polini CP EVO 19mm carburetor manual choke spigot	EVO spigot	Strong sport setups where you still want usable throttle response.	View product
21mm	Polini CP EVO 21mm carburetor manual choke spigot	EVO spigot	Tuned 70cc setups with a matching intake and exhaust.	View product
24mm	Polini CP EVO 24mm carburetor manual choke spigot	EVO spigot	High-performance and race-style engines that can use high airflow.	View product

Polini CP clamp manual choke carburetors

Size	Product	Mounting style	Best use	Shop
15mm	Polini CP 15mm carburetor manual choke clamp connection	Clamp	Mild 50cc setups and street builds where easy response matters.	View product
17.5mm	Polini CP 17.5mm carburetor manual choke clamp connection	Clamp	Sport 50cc and mild 60cc or 70cc street setups.	View product
19mm	Polini CP 19mm carburetor clamp connection manual choke	Clamp	A strong all-round choice for many tuned Puch engines.	View product
21mm	Polini CP 21mm carburetor clamp connection manual choke	Clamp	Stronger sport setups with enough cylinder and exhaust to use the airflow.	View product

Polini CP spigot manual choke carburetors

Size	Product	Mounting style	Best use	Shop
17.5mm	Polini CP 17.5mm carburetor manual choke spigot	Spigot / rubber connection	Street and sport setups using a rubber intake connection.	View product
19mm	Polini CP 19mm carburetor manual choke spigot	Spigot / rubber connection	Sport street setups where vibration isolation and flexible fitment help.	View product
21mm	Polini CP 21mm carburetor manual choke spigot	Spigot / rubber connection	Tuned engines with the intake and exhaust to support more flow.	View product

Polini CP carburetor sets and extra options

Size	Product	Mounting style	Best use	Shop
17.5mm	Polini CP 17.5mm carburetor manual choke replica spigot	Replica spigot	Budget-friendly replacement-style option for smaller street and sport setups.	View product
21mm	Polini CP 21mm carburetor cable choke clamp connection with air filter	Clamp with cable choke and air filter	Useful when you want a complete carburetor and air filter combination with cable choke operation.	View product
21mm	Polini CP 21mm carburetor manual choke spigot with air filter	Spigot with manual choke and air filter	Useful when your setup needs a spigot CP carburetor and matching air filter in one kit.	View product

For related jets, manifolds, filters and spare parts, you can also browse the Polini CP / PWK parts category.

Clamp, spigot and EVO spigot: what is the difference?

The carburetor size is only one part of the choice. You also need the correct mounting style for your intake manifold and frame clearance.

Polini CP clamp

A clamp-style CP carburetor tightens directly around the intake manifold. This can be a clean solution when your manifold and carburetor connection are designed for that style.

Good when your intake manifold matches the clamp size.
Useful for mild and sport street setups.
Simple mechanical connection.
Check frame clearance for the filter, throttle cable and choke.

Polini CP spigot

A spigot-style CP carburetor slides into a rubber or flexible intake connection. This style is common on tuned engines because it can reduce vibration transfer and gives more flexibility with manifold design.

Good when your manifold uses a rubber connector.
Helps with vibration isolation.
Useful for sport street setups and stronger engines.
Allows more flexible carburetor positioning.

Polini CP EVO spigot

The EVO spigot versions are the more performance-oriented CP options in the Puchshop range. These are available in 19mm, 21mm and 24mm.

Best for engines built to make power at higher rpm.
Needs a cylinder, exhaust and intake that can actually use the extra airflow.
Requires more careful jetting than a mild street carburetor.
Best suited for fast sport or race-style setups.

Which Polini CP size should you choose?

Venturi size matters. A larger venturi can reduce restriction and support more power when the engine can use the airflow. A smaller venturi increases air speed and can improve response in the useful rpm range. That means the best carburetor is not automatically the biggest carburetor. The best carburetor is the one that matches your engine.

CP size	Good starting point for	Character
15mm	Mild 50cc setups and small street builds	Easy response, simple street behavior and not a big top-end carburetor.
17.5mm	Sport 50cc and mild 60cc or 70cc setups	Good balance of response, tuning range and street usability.
19mm	Strong 50cc and sport 60cc or 70cc setups	Often a strong all-round choice for tuned Puch engines.
21mm	Tuned 70cc setups with matching exhaust and intake	More airflow and stronger top-end potential, but it needs careful jetting.
24mm	High-performance or race-style setups	Best for engines that can use high airflow and higher rpm.

Practical Puch recommendation: For most street-tuned Puch mopeds, start by looking at 17.5mm or 19mm. For a stronger 70cc setup with a good exhaust, intake and ignition setup, a 21mm Polini CP can make sense. For a serious race-style setup, the 24mm Polini CP EVO spigot can be the right choice, but it is usually too much carburetor for a mild street engine.

How the Polini CP tuning circuits work

A Polini CP carburetor does not run on one jet alone. Different parts of the carburetor affect different throttle positions and engine loads.

Part	When does it mainly work?	What can you notice with the wrong setup?
Float and float needle	Constantly, because the float bowl fuel level affects every fuel circuit	Overflowing, flooding, inconsistent mixture or fuel starvation.
Idle jet	Idle, closed throttle and the first throttle opening	Bad idle, stalling, hanging idle or poor response from low rpm.
Air screw	Idle and low throttle progression	Poor pickup from idle, unstable idle or low-speed lean/rich symptoms.
Throttle valve	Controls the available airflow area as the throttle opens	Uneven first response, poor airflow control or incorrect idle speed if not closing correctly.
Conical needle	Low-to-mid, midrange and acceleration	Hesitation, bogging, rich blubbering or lean surging at partial throttle.
Atomizer / nozzle bush and air brake jet	Fuel-air emulsion through the needle and main system	Hard-to-correct midrange mixture, poor atomization or an engine that feels wrong even with jet changes.
Main jet	High throttle and full throttle	Lean running, overheating, four-stroking, poor pulling power or piston damage if too lean.

Float and fuel level

The float system keeps fuel in the float bowl at a controlled level. On a Polini CP, the float lever arm is calibrated during assembly and is not meant to be adjusted like some other carburetors.

Idle jet and air screw

The idle jet controls fuel when the throttle is closed or almost closed. It also affects the first response when you open the throttle. The air screw fine-tunes the idle and low-throttle mixture. On the Polini CP, screwing the air screw in reduces the air supply and enriches the mixture. Screwing it out increases air and leans the mixture. A basic starting point is about 1 to 1.5 turns open from fully closed.

Conical needle, atomizer and air brake jet

The Polini CP is a needle-type carburetor. As the throttle slide lifts, the conical needle changes the fuel passage through the atomizer. The atomizer and air brake jet influence how fuel and air mix before entering the engine. This makes the CP tunable, but it also means midrange tuning should be done logically and step by step.

Main jet

The main jet controls fuel delivery at larger throttle openings and full throttle. Start with a safe rich main jet and work down carefully. A lean two-stroke setup can overheat, seize or damage the piston.

Polini CP air brake jet explained

The air brake jet is part of the Polini CP atomizer system. The atomizer is the tube that connects the main jet area to the venturi. Fuel is drawn through the main jet and needle area, while air from the air channel helps mix and pre-atomize that fuel before it is pulled into the engine.

Polini explains in its official CP carburetor instructions that the CP can be set up to work with different atomizer behavior by changing the brake air jet. A closed air brake jet makes the system behave like an atomizer without holes. An open air brake jet lets the atomizer holes work and makes the mixture weaker, or leaner.

Air brake setup	What it does	What you may notice
Closed air brake jet	Makes the atomizer system behave more like an atomizer without holes.	Useful as a baseline when you do not want extra air leaning the atomizer system.
Open air brake jet	Allows the atomizer holes to work and adds air to the fuel emulsion.	Can make the low-to-mid and mid-throttle mixture weaker or leaner.

That is why the air brake jet matters when a Polini CP idles correctly and pulls at full throttle, but feels rich, soft, blubbery, or inconsistent in the low-to-mid and mid-throttle range. The air brake jet is not the same adjustment as the air screw: the air screw works on idle and low-throttle progression, while the air brake jet affects the atomizer and needle/main fuel emulsion.

Do not use the air brake jet as the first tuning step.

First check for false air, fuel flow and float condition.
Check air filter restriction, intake length and fuel hose routing.
Start with a safe main jet before testing hard under load.
Set the idle jet, air screw and needle clip before chasing advanced atomizer changes.

If the low-to-mid range still cannot be cleaned up with normal jetting changes, then the air brake jet, atomizer and nozzle bush become advanced tuning areas.

Practical rule: leave the standard air brake setup alone until the basic carburetor settings are close. Change only one thing at a time, test with a warm engine and keep a safe rich main jet while you are learning what the setup wants.

Interactive Polini CP tuning tool

Use the slider below to see which Polini CP carburetor parts have the strongest influence as the throttle opens. This is a simplified learning tool, not a replacement for real test riding, plug checks, temperature checks and safe jetting.

Interactive Polini CP Tuning Simulator

Twist the throttle below to see how the Polini CP idle circuit, throttle slide, needle and atomizer system, air brake jet and main jet hand off fuel-metering responsibility as throttle opening and engine load increase.

Idle Jet & Air Screw Throttle Slide Needle, Atomizer & Air Brake Main Jet

Twist the throttle: 0% (Standgas)

Active Polini CP components

Leerlaufdüse & LuftschraubeGeschätzter Einfluss: 100%
Kontrolliert Standgas und sehr kleine Gasöffnungen. Beim Polini CP beeinflussen Leerlaufdüse und Luftschraube Startverhalten, Standgasqualität und die erste Gasannahme aus geschlossenem Gas stark.
GasschieberGeschätzter Einfluss: 0%
Beeinflusst die erste Gasannahme, indem er verändert, wie viel Luft beim ersten Öffnen des Gases einströmen kann. Das ist die direkte Verbindung zwischen Gasgriff und Luftstrom durch den Venturi.
Konische Nadel, Zerstäuber & Air BrakeGeschätzter Einfluss: 0%
Dosiert Kraftstoff bei Teillast und Beschleunigung. Die konische Nadel arbeitet im Zerstäuber, während die Air-Brake-Düse die Kraftstoff-Luft-Emulsion im unteren bis mittleren Gasbereich beeinflussen kann.
HauptdüseGeschätzter Einfluss: 0%
Wird bei viel Gas bis Vollgas zum dominanten Kraftstoffkreis und kontrolliert den maximalen Kraftstofffluss unter hoher Motorlast. Starte sicher fett und arbeite dich vorsichtig nach unten.

Constant systems

Float and float needle: Controls the fuel level inside the float bowl. On a Polini CP, the fuel level affects the mixture signal at the nozzles, so a dirty float needle, wrong float condition or fuel supply issue can affect every throttle range.

CP tuning note: The Polini CP uses a conical needle, atomizer and air brake system. Start safely rich, make one change at a time and test with the engine fully warm.

Basic Polini CP tuning order

Tuning works best when you follow a clear order. Do not change everything at once, and do not tune around a dirty carburetor, poor fuel flow, false air or ignition problems.

Basic Polini CP tuning order:

Choose the correct carburetor size and mounting type for your cylinder, exhaust, intake and riding style.
Check physical fitment so the carburetor, air filter, throttle cable, choke and fuel hose do not hit the frame or engine parts.
Make sure the carburetor is clean and fuel flow from the tank is strong enough.
Start with a safe main jet so the engine does not run dangerously lean.
Set the air screw baseline around 1 to 1.5 turns out from fully closed.
Warm up the engine before making final decisions.
Set idle speed with the idle screw.
Tune low-throttle response with the idle jet and air screw.
Tune midrange with the needle clip and, when needed, the needle or atomizer setup.
Tune full throttle with the main jet, then recheck after riding.

Important: Always tune from rich toward correct. A two-stroke Puch engine that runs too lean can overheat, seize or damage the piston.

Common Polini CP symptoms and what to check

Carburetor symptoms can overlap with ignition, air leaks, exhaust restriction and fuel supply problems. Use the table below as a starting point, then check the complete engine setup.

Symptom	Likely area to check	What it can mean
Engine starts badly when cold	Choke / starter circuit, idle jet, air screw	Not enough enrichment or poor low-speed setup.
Engine stalls when you open the throttle	Idle jet too rich, needle too rich, poor fuel atomization	The engine may be loading up before it can clean out.
Idle hangs high before settling	Idle jet too small, air screw too far out, air leak	The low-throttle mixture may be too lean.
Engine bogs at low throttle	Idle jet, air screw, needle position	The low-speed circuit is not matched to the engine.
Engine four-strokes or blubbers at full throttle	Main jet too large, needle too rich	Too much fuel at higher throttle openings.
Spark plug is light grey or white	Main jet too small, lean setup, air leak	Dangerous lean condition. Stop and correct before riding hard.
Spark plug is wet or sooty	Main jet too large, rich needle, weak ignition	Too much fuel or incomplete combustion.
Fuel leaks from the carburetor	Float needle, float, dirt in fuel system	Fuel supply may not be shutting off correctly.
Good idle but poor midrange	Needle clip, needle type, atomizer, air brake jet	The mid-throttle circuit needs adjustment.
Good low rpm but weak top-end	Main jet, carb size, exhaust, intake restriction	The engine may need more fuel, more airflow or a better matched setup.

Fitting tips before you ride

Before starting the engine, check that the carburetor is properly fitted and that the throttle and choke operate smoothly.

The carburetor is tight on the manifold.
The throttle slide opens fully and snaps closed.
The throttle cable has a little free play.
The choke opens and closes fully.
The fuel hose is not kinked.
The carburetor does not touch the frame, cylinder, engine case or side cover.
The air filter is fitted securely.
The fuel flow from the tank is strong enough.
The engine has no intake air leaks.

Fitment note: Polini CP carburetors can have different dimensions than more common carburetors. Check filter flanges, throttle cable routing and choke cable routing during installation.

Ready to upgrade your intake?

Find the right Polini CP carburetor and the exact jets, manifolds and filters you need to get your Puch running properly.

View all Polini CP carburetors Start with the right carburetor size, then tune safely from rich toward correct.

FAQ: Polini CP carburetors for Puch mopeds

Is a Polini CP better than a Dellorto PHBG?

It depends on the setup. A Dellorto PHBG is very common and has a large tuning-parts ecosystem. A Polini CP is compact, modern and available in useful performance sizes. For many tuned Puch engines, the CP is a strong option when you choose the correct size and mounting style.

What Polini CP size is best for a Puch Maxi?

For many street-tuned Puch Maxi setups, 17.5mm or 19mm is a good place to start. A 21mm carburetor can work well on stronger 70cc setups. A 24mm CP EVO is usually better suited to high-performance or race-style engines.

Should I choose clamp or spigot?

Choose the mounting style that matches your intake manifold. A clamp carburetor tightens directly to the manifold. A spigot carburetor usually mounts into a rubber connection. Spigot mounting can help with flexibility and vibration isolation on tuned setups.

What is the basic air screw setting on a Polini CP?

A good basic starting point is 1 to 1.5 turns open from fully closed. From there, adjust the air screw after the engine is warm and the idle jet is close to correct.

What does the air brake jet do on a Polini CP?

The air brake jet changes how air reaches the atomizer system. A closed air brake jet keeps the atomizer behavior closer to a no-hole atomizer, while an open air brake jet lets the atomizer holes work and leans the mixture. It mainly matters when you are chasing low-to-mid and mid-throttle behavior after the basic jetting is close.

Should I change the air brake jet first?

No. Start with the basics first: clean carburetor, no false air, correct fuel flow, safe main jet, suitable idle jet, air screw setting and needle clip. Only look at the air brake jet, atomizer and nozzle bush when the normal tuning steps do not clean up the midrange.

Should I start with a rich or lean main jet?

Start rich and tune down carefully. Beginning with a larger main jet helps reduce the risk of lean damage, then you can test and reduce step by step.

Can I use a 24mm Polini CP on a 50cc Puch?

You can use a large carburetor only if the rest of the engine setup can use it. On most mild 50cc street engines, a 24mm carburetor is usually too large and can reduce throttle response. It makes more sense on a high-rpm racing

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