BGM PRO Touring Evo rotary-valve crankshaft with 60 mm stroke and 128 mm connecting rods for Quattrini M244, VMC Explorer 244, and Polini 244— no need to bore out the stock PX200 crankcase, with forged crank arms and forged connecting rods.
The BGM PRO Touring Evo crankshaft BGM031128G combines a 60-mm stroke with an exceptionally long 128-mm connecting rod —and fits into a stock PX200 crankcase without requiring the crank chamber to be bored out for the crankshaft. It thus combines modern 244-cm³ long-connecting-rod designs with a key practical advantage: the original engine block can be retained.
At the same time, the crankshaft assembly is consistently designed for high load-bearing capacity. The crankshaft journals and connecting rods are forged. The forging process produces a favorable grain orientation tailored to the component’s geometry and a highly resilient microstructure—an excellent foundation for high toughness, fatigue strength, and resistance to bending and torsional stresses. In the Evo version, this is complemented by a precise press fit and additional chemical hardening of the crankpin.
Typical applications include the Quattrini M244, the VMC Explorer 244, and the Polini 244. The long connecting rod provides additional flexibility regarding cylinder position, compression edge, and valve timing angles. At the same time, the conventional PX coupling stub allows for a free choice among the standard compatible PX coupling systems.
Another key design feature is the intake layout. The crankshaft flange features a very deeply machined intake shoulder in the area below the rotary valve intake. This provides a large free cross-sectional area early on when the rotary valve is open. This allows for a high effective intake cross-sectional area to be achieved without having to generate the required flow rate solely through extremely long intake valve timing.
No spindling on the PX200 housing Forged crankshaft journals Forged connecting rod 60 mm stroke 128 mm connecting rod Quattrini M244 VMC Explorer 244 Polini 244 Evo connecting rod lock Deep intake shoulder
One of the most important design advantages of the BGM031128G lies in its external dimensions. Although the crankshaft combines a 60 mm stroke with a very long 128 mm connecting rod, the stock PX200 crankcase remains unchanged. The PX200 engine block does not need to be bored out or enlarged in diameter to accommodate the crankshaft itself.
This is a decisive advantage, especially with high-quality original crankcases: it eliminates the need for an irreversible machining step on the crankcase. At the same time, the foundation for large-displacement cylinders such as the Quattrini M244, VMC Explorer 244, and Polini 244 is preserved. Machining on the cylinder and intake sides may still be necessary depending on the desired setup; the advantage specifically refers to the free movement of the crankshaft within the PX200 crankcase.
The crankshaft journals and connecting rods of the BGM PRO Touring Evo are forged. During forging, the material is plastically deformed under high pressure. This results in a favorable grain orientation that follows the component’s contour, which is particularly advantageous for components subjected to high alternating stresses, such as crankshaft journals and connecting rods.
The key factor here is not a supposedly higher steel density, but rather the load-bearing microstructure and the oriented grain orientation. This provides an excellent foundation for high strength, toughness, and fatigue strength, as well as resistance to bending and torsional forces. This is a significant design advantage, particularly for large-displacement two-stroke engines with high combustion pressures, severe load cycles, and long full-load phases.
The 128-mm connecting rod length makes the BGM031128G particularly suitable for cylinders whose geometry is specifically designed for a long connecting rod.
| Cylinder | Compatibility with BGM031128G |
|---|---|
| Quattrini M244 | A very typical application for a 60-mm stroke and a long connecting rod; spacers allow for precise positioning of the cylinder. |
| VMC Explorer 244 | Suitable for long-connecting-rod 244-cm³ setups with a 60 mm stroke and variable cylinder position. |
| Polini 244 | Polini specifies 60/127 as standard. The BGM031128G provides a 60 mm stroke and 128 mm connecting rod; the additional 1 mm connecting rod length is accounted for via the cylinder position or appropriate spacers. |
Compared to the standard 110-mm PX200 connecting rod, the 128-mm connecting rod is exceptionally long. While the stroke remains unchanged at 60 mm, the geometric relationship between the crankshaft radius, connecting rod, and piston changes significantly.
Of particular importance to the engine builder is the additional freedom in cylinder positioning. With appropriate base spacers and, if necessary, head spacers, the cylinder can be positioned higher or lower. This alters the opening and closing points of the intake and exhaust valves.
This point is particularly interesting with the Polini 244: The cylinder is originally designed for a 127-mm connecting rod. The 128-mm connecting rod from the BGM031128G provides an additional millimeter of design leeway, which can be utilized or compensated for via the spacer configuration. This allows the final cylinder position to be more precisely tuned to the desired valve timing concept.
In a rotary vane engine, it is not just the pure intake duration that determines how well the engine is filled. Equally important is the effective cross-sectional area that is open while the intake is open.
This is precisely where the layout of the BGM PRO shaft comes into play. In the area below the intake port, the crankshaft web is deeply recessed. This deep intake shoulder creates plenty of free space right where the mixture flows from the intake manifold into the crankcase.
The result is a large usable intake cross-sectional area even at moderate rotary valve times. This makes it possible to build a high-performance engine without necessarily having to close the intake very late.
On a typical PX200 engine case, the BGM PRO Touring Evo cam closes the rotary valve intake approximately 58° after TDC. The actual value depends on the engine case used and its intake port.
For a performance-oriented yet rideable street engine, an intake start of approximately 120° before TDC has proven effective as a starting point. The necessary machining is performed on the intake port of the engine block.
The combination of moderate opening duration and the deep intake shoulder of the crankshaft is a deliberate choice: It is not merely the maximum number of degrees of intake timing that generates flow, but rather a large effective cross-sectional area during the open phase.
The long connecting rod alters the geometry of the crankshaft assembly. With a 60-mm stroke, the crankshaft radius is 30 mm. The ratio of crankshaft radius to connecting rod length is approximately 0.234 for a 128-mm connecting rod; with a standard 110-mm connecting rod, it is approximately 0.273.
With the same crankshaft geometry, the longer connecting rod reduces the lateral angle of the connecting rod relative to the cylinder. This can reduce lateral forces on the piston and contributes to a mechanically favorable crankshaft assembly. However, the actual smoothness of an engine’s operation also depends on balancing, piston weight, ignition, clutch, flywheel, and the overall engine design.
The designation “Touring Evo” denotes the current stage of development within the BGM PRO Touring series. The focus is not on a single detail change, but rather on the manufacturing of the complete crankshaft assembly, which has been refined over the years.
Particular emphasis is placed on the connection between the crankshaft journals and the crankpins. In addition to the precisely defined press fit, the crankpin is chemically secured with a high-strength anaerobic Loctite adhesive. This additional securing measure increases the crankshaft journals’ resistance to twisting under high loads and makes the Evo version particularly suitable for high-performance, high-torque engines.
Within the well-known BGM PRO Touring product line, the “Evo” designation thus represents not merely a cosmetic model update, but a concrete technical advancement in manufacturing and joining technology.
The BGM PRO Touring Evo crankshafts are constructed with forged crank webs. The connecting rod is also forged. The key advantage lies in the grain orientation—which is shaped by the forging process and aligned with the component’s geometry—and in the microstructure, which is highly resilient for components subjected to high cyclic loading.
Just as important as the base material is the connection between the crankshaft journals and the main bearings. The manufacturing and assembly processes for BGM PRO crankshafts have been continuously refined over the years. In addition to a precisely defined press fit, the journal is now also secured with a high-strength anaerobic bonding adhesive from Loctite.
This additional chemical lock complements the mechanical press fit and enhances protection against twisting of the crankarms under high loads. Together with the forged components, this results in a particularly rigid and durable crankshaft assembly for large-displacement engines with high torque, severe load cycles, and performance-oriented applications.
The lower connecting rod bearing is supplied with fuel mixture via two large lubrication slots and additional lateral lubrication areas. Together with the racing bearing and the lateral thrust washers, this creates a connecting rod bearing assembly designed for high load capacity.
The upper connecting rod bearing is supplied through two lubrication holes. An INA piston pin bearing is included in the scope of delivery.
The connecting rod is designed for a piston pin with a Ø16 mm diameter. This means the rod fits directly onto corresponding pistons in modern large-frame cylinders.
If a piston with a 15-mm piston pin is to be used, this can be achieved with a conversion piston pin bearing designed for this purpose.
On the clutch side, the BGM031128G uses the conventional PX mounting. This is particularly interesting when used with the Polini 244: Polini’s own 60/127 shaft features special splines and is designed to fit a corresponding Polini clutch hub.
With the BGM PRO shaft, however, you retain the freedom to choose from the standard clutch systems compatible with the PX200 crankshaft stub.
The BGM PRO Touring crankshaft has been in use for years in numerous high-performance PX200 engines. Real-world setups with over 30 PS and more than 35 Nm of torque demonstrate that the crankshaft functions reliably even with significantly increased engine power.
The combination of forged crankshaft journals, a forged connecting rod, high-quality connecting rod bearings, and the precise, chemically treated main journals provides an exceptionally robust foundation for this. It is precisely this manufacturing quality—refined over the years—that makes the crankshaft appealing not only for classic touring engines but also for very high-performance street and sport setups.
For high-performance engines, we also recommend a properly balanced rotating mass. A pole wheel weighing up to approximately 2,300 g has proven to be an excellent combination of smooth operation, responsiveness, and low dynamic stress in our setups.
| Manufacturer | BGM PRO |
|---|---|
| Part Number | BGM031128G |
| Type | Touring Evo Rotary Valve Crankshaft |
| Evo Version | Current evolution stage with advanced joining technology and additional chemical connecting rod pin reinforcement |
| Stroke | 60 mm |
| Connecting rod length | 128 mm |
| Standard PX200 connecting rod length for comparison | 110 mm |
| Piston pin | Ø16 mm |
| Ø15-mm piston pin | Possible with a suitable conversion piston pin bearing |
| Intake control | Rotary valve |
| Cheek width | PX200 design |
| PX200 crankcase | No need to bore out the standard crankcase for the crankshaft |
| Intake layout | Deep intake shoulder for large clear cross-section |
| Intake Closure | Approx. 58° after TDC on a typical PX crankcase, depending on the crankcase |
| Recommended intake start as a tuning starting point | Approx. 120° before TDC |
| Crankpin | Forged |
| Connecting rods | Forged |
| Connecting pin joint | Precision press fit with additional chemical locking using high-strength Loctite adhesive |
| Upper connecting rod bearing | INA piston pin bearing included |
| Clutch housing | Conventional PX200 crankshaft stub |
| Typical cylinders | Quattrini M244, VMC Explorer 244, Polini 244, and comparable 60-mm long-connecting-rod designs |
| Vehicles | Vespa PX200, Rally200 with Ducati ignition, Cosa200, Motovespa TX200 |
| Additional Applications | Appropriately prepared or bored-out 80–150-cm³ large-frame casings |
The BGM PRO Touring Evo BGM031128G combines two features that are particularly important in modern 244-cm³ large-frame designs: a 60-mm stroke with 128-mm long connecting rods without boring out the stock PX200 crankcase , and a forged crankshaft system consistently designed for high load capacity.
This makes the crankshaft an excellent basis for the Quattrini M244, VMC Explorer 244, Polini 244, and comparable designs. The long connecting rod offers additional flexibility in cylinder positioning and the selection of valve timing angles; at the same time, the conventional PX clutch stub provides a wide range of compatible clutch systems.
Of particular interest is the deeply machined intake shoulder on the crankshaft journal: it provides a large amount of free cross-sectional area directly below the rotary valve intake. This allows for high-performance setups without having to rely solely on extremely long intake valve timing to achieve the required flow rate. This makes the crankshaft particularly attractive for powerful yet still drivable street engines.
Added to this is the crankshaft assembly’s manufacturing process, which has been refined over the years. The crankpin is not only precisely press-fit but also chemically secured with high-strength Loctite adhesive. Together with the forged components and the sophisticated bearing arrangement, this results in a crankshaft that has proven itself convincingly even in high-performance, high-torque setups.
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