Cylinder comparison Vespa PX200 - Malossi Sport 210 - VMC Ranger 213 - Quattrini M244

Is this actually durable?

If you are not yet deeply rooted in the Vespa scene, you will probably ask yourself in advance: “Is all this really worth it – and will it last?” The 200 cc Vespa engines in particular have the reputation of being indestructible and are often used for round-the-world trips.

Is the engine still just as durable after a conversion? Our clear answer: a definite yes. We are not saying this because we want to sell products, but out of sheer conviction. We ourselves ride engines like this every day. It quickly adds up to 10,000 km and more per year – under full load, not cruising gently.

What matters to us: When we talk about an increase in power, the result must be usable in the long term. For this reason, instead of the term “tuning”, we prefer to talk about “conversion”. In the true sense, tuning means fine adjustment – in everyday language, however, it often stands for crude modifications aimed solely at peak power.

A well-converted engine therefore not only includes the power-increasing parts, but above all the components that improve durability and safety: clutch, crankshaft, gaskets as well as tyres and brakes.

The 200 cc engines are based in design terms on the old 125/150 cc engines. You might think that, with standard displacement and power output, they are already at their limit. Fortunately, these engines were designed back then with large safety reserves. The result: This engine concept can cope with a significant increase in power without complaint – provided the engine is built properly and fitted with high-quality components.

Durability conclusion: If you overhaul carefully and do not save money in the wrong places, you will enjoy a significantly more powerful engine for a long time.

Recommendations for a durable conversion

Crankshaft

The central component of a solid conversion is the choice of crankshaft. In a Vespa rotary valve engine it not only provides stroke, but also largely defines the inlet timing.

The stock PX200 crankshaft from Piaggio is very robust and can handle around 20 hp permanently. In practice, however, most original cranks already have many kilometres and long periods of inactivity behind them – which takes its toll on the big end bearing. On top of that, the inlet timing of the stock crank is extremely conservative.

A BGM PRO Touring crankshaft solves several problems at once: high-alloy forged steel instead of simple case-hardened steel, precisely machined bearing surfaces, forged conrod with silver steel cages, widened inlet web, larger oil seal seat and a specially secured crank pin. Together with an inlet profile optimised in many tests, it forms an extremely solid basis for strong touring engines.

Clutch

To put the increased power onto the road in a controllable way, an uprated clutch is practically mandatory. In principle, both the old 7-spring type and the later Cosa clutch can be adapted – but often at the cost of high lever effort or increased wear on hub and basket.

A BGM Superstrong clutch is a clear recommendation here: designed for well over 40 hp, can be fine-tuned to the intended use via the choice of springs and is still easy to operate. A sports clutch with an extremely wide usable range – without the pitfalls of a pure racing clutch.

Gaskets and oil seals

The be-all and end-all of a clean engine build are high-quality gaskets. BGM PRO oil seals use FKM/Viton®, are alcohol-resistant and very durable. In combination with the BGM PRO engine gaskets made of high-quality gasket paper with a silicone coating, the engine remains leak-free and reliable in operation over the long term.

Primary drive / cush drive

The primary drive between clutch and gearbox is designed at the factory for around 12 hp. With a strong cylinder, this power quickly doubles – including significantly higher torque peaks.

The cush drive springs of the primary drive must be matched to this additional load, otherwise load peaks are passed on unfiltered to the gearbox. Reinforced BGM PRO primary springs are available as an upgrade kit with plates and rivets. If you also want to change the overall gearing, you can choose the straight-cut BGM PRO primary drive. It relieves the engine casing of axial forces and, thanks to its special tooth profile, is still as quiet as the original helical gear.

Ignition

The stock PX ignition is basically excellent and can be retained. In combination with a BGM PRO flywheel or a BGM PRO ProRev ignition, overall performance can be improved even further – while maintaining a stable ignition characteristic.

What you should not do

Install a cylinder “plug & play” into a non-overhauled engine

For the cylinders presented here to realise their potential, a larger effective inlet time-area is essential. With a stock crankshaft and unmodified inlet window, you not only lack peak power, but also low-end torque and pull.

On top of that, the true mileage of an old original crank is usually unknown. Any increase in power should therefore always be based on a freshly overhauled engine. Defective oil seals can otherwise lead to air leaks, a lean mixture and engine damage. BGM PRO engine overhaul kits provide a solid foundation here.

In the same step, the rotary valve inlet can be adjusted. This is not strictly necessary if you are not chasing the last horsepower. Touring-capable PX200 engines run very well with inlet timings of around 110–120° before TDC and 55–70° after TDC. The important factor is the effective time-area – not the exact degree figure after the decimal point.

Blindly fitting a large carburettor

The very short inlet tract of PX engines, combined with the asymmetrical rotary valve, allows comparatively small carburettor cross-sections. The stock SI 24/24 is absolutely sufficient for 99 % of touring setups – even well over 30 hp have already been achieved with it.

Carburettors with 30 mm and more usually require a significantly longer intake tract due to space constraints – the advantage of the larger cross-section is thus partly eaten up again. Even an SI 28 often brings only a small increase in performance compared with the SI 24 as long as the inlet is not heavily reworked.

For a start, it is advisable to keep the stock air filter. It restricts surprisingly little, yet provides a very forgiving base for jetting. If you remove it and replace it with a bellmouth, the air correction must be adjusted accordingly – otherwise there is a risk of lean running under load.

Engine build – how much wrenching experience do you need?

Anyone who feels confident overhauling an engine can also implement the engine concepts presented here. In principle, with none of the three conversion cylinders is machining of the engine casing strictly necessary. If you want to optimise performance, you can additionally work on the inlet tract – but it is not mandatory.