High-quality 60-mm long-stroke crankshaft with 115-mm race connecting rods for high-performance Vespa Wideframe engines—specially developed for the LARCHOTEK Dolomiti 187 cylinder kit.
The LARCHOTEK Passo Rolle Signature was developed specifically for high-performance Vespa Wideframe engines and, in particular, for use with the LARCHOTEK Dolomiti 187 cm³ cylinder kit. With a 60 mm stroke and 115 mm connecting rod length, it precisely matches the geometric design of the Dolomiti concept.
This means the Passo Rolle is not just any long-stroke crankshaft that happens to be compatible with the cylinder. The crankshaft and cylinder are designed as a unified system. As a result, the stroke, connecting rod length, and cylinder geometry can be precisely matched from the outset.
The Signature version also features a particularly high-quality race-spec connecting rod. Especially in a large-displacement wide-frame engine with significantly increased power and high torque, the quality of the connecting rod is a key factor in ensuring a durable and robust engine build.
60 mm long-stroke 115 mm connecting rod Race connecting rod Precision-balanced Piston pin Ø15 mm Dolomiti 187 Wideframe Faro Basso Touring & Sport
A key feature of this version is the high-quality 115-mm race connecting rod. In the classic stock engine, the load on the crankshaft is relatively manageable. However, with a displacement of 187 cm³ and a significantly increased torque level, the demands change considerably.
With every power stroke, the connecting rod transmits the combustion forces from the piston to the crankpin and the crank arms. At the same time, as RPM increases, high dynamic forces are generated by the movement of the piston and connecting rod.
A high-performance crankshaft must therefore be capable of more than simply having the correct geometric dimensions. In the Signature version, the quality of these heavily loaded components is also a top priority.
The Passo Rolle Signature is delivered precision-balanced. Especially with a 60-mm long-stroke crankshaft for a high-performance wide-frame engine, balancing is a crucial part of the overall design.
Careful balancing cannot completely eliminate the mass forces inherent in the design of a single-cylinder two-stroke engine. However, it helps prevent additional imbalance and achieve the smoothest possible engine operation.
This is particularly relevant for a touring engine, which is designed to perform smoothly not only during short bursts of acceleration but also over longer distances and across a wide range of engine speeds.
The Passo engine features a crankshaft stroke of 60 mm. Combined with the Dolomiti cylinder’s 63-mm bore, this results in a displacement of approximately 187 cm³.
The 60-mm stroke is not merely a means to an end for increasing displacement. It is an essential component of the engine’s character. This displacement concept supports the powerful torque delivery typical of the Dolomiti and enables a high-performance engine that does not have to rely exclusively on high RPMs.
| Component | Dimension | Meaning |
|---|---|---|
| Crankshaft stroke | 60 mm | Long-stroke design for the Dolomiti 187 concept |
| Connecting rod length | 115 mm | Matched to the intended cylinder and piston geometry |
| Cylinder bore (Dolomiti) | Ø63 mm | Combined with a 60 mm stroke, this results in approximately 187 cm³ |
| Piston pin | Ø15 mm | Compatible with the intended piston and connecting rod design |
| Piston pin bearing | 15 × 19 × 20 mm | Matching needle bearing for the piston pin |
The connecting rod length of 115 mm is part of the Dolomiti system’s design. Cylinder height, piston position, and crankshaft geometry are all optimized for this combination.
When assembling the engine, therefore, one should not focus solely on the correct crankshaft stroke. The connecting rod length is also a critical dimension. A different connecting rod length alters the piston position in the cylinder and thus the entire geometric configuration.
The Passo Rolle Signature offers a 60 mm stroke and 115 mm connecting rod —exactly the combination intended for the Dolomiti.
The Passo Rolle is designed as a direct-intake crankshaft for the corresponding wide-frame engine configuration. In the Dolomiti 187, fresh gas control is managed via the cylinder’s diaphragm intake.
As a result, the crankshaft does not prioritize the classic intake control via a rotary valve. Rather, the crankshaft is an integral part of the complete diaphragm and long-stroke concept.
One of the greatest advantages of the Passo Rolle Signature is that it does not need to be retrofitted to an existing cylinder. It was specifically developed for the LARCHOTEK Dolomiti 187 cylinder kit.
As a result, the crankshaft stroke, connecting rod length, and cylinder geometry form a defined system. This facilitates a technically sound assembly, especially in a high-performance classic engine.
We were able to see for ourselves just how far modern wideframe technology has come at our Scooter Center Open Day. With Ahron Larcher’s Dolomiti wideframe, we measured up to 25.5 PS at the wheel and 27.2 Nm on our test bench.
These figures illustrate the forces a modern wide-frame crankshaft must transmit. The engine’s character is particularly noteworthy: peak torque was already available at around 6,200 rpm, and maximum power at just under 6,900 rpm.
So it’s not just about high RPM or a single peak value. It is precisely the high torque of such a street engine that places considerable demands on the crankshaft, connecting rods, and bearings.
This is exactly where the Passo Rolle Signature comes in: It forms the crankshaft base—specially tuned to the Dolomiti system—for a modern, high-performance wide-frame engine.
The Passo Rolle Signature is designed for compatible classic Vespa wide-frame engines with a displacement of 125 to 150 cm³ and is specifically tuned for use with the LARCHOTEK Dolomiti 187.
| Series | Frame prefix | Time Period | Note |
|---|---|---|---|
| Vespa 125 Wideframe | VM | approx. 1953–1954 | Check the engine base and existing components before assembly |
| Vespa 125 Wideframe | VN | approx. 1954–1957 | Check the engine base and existing components before assembly |
| Vespa 150 Wideframe | VL1T | from approx. 1954 | For the corresponding wide-frame engine configuration |
| Vespa 150 | VB1T | approx. 1957–1958 | For compatible wide-frame engine configuration |
| Vespa Wideframe | VGL1T | 1950s | Check the engine base before installation |
The crankshaft is also designed for compatible ACMA Wideframe engines. Since historic licensed models may differ in detail depending on the year of manufacture and version, the existing engine base should be checked before assembly.
In historic vehicles, different engine cases or previously modified components may have been installed over the decades. The actual engine base should therefore always be checked directly on the vehicle or engine case before assembly.
| Manufacturer | LARCHOTEK |
|---|---|
| Model | Passo Rolle Signature |
| Engine Type | Vespa Wideframe 125–150 cm³ |
| Crankshaft Type | Direct intake |
| Stroke | 60 mm long stroke |
| Connecting rod length | 115 mm |
| Connecting Rod Design | High-quality race connecting rod / Signature design |
| Piston pin | Ø15 mm |
| Piston pin bearing | 15 × 19 × 20 mm |
| Balancing | Precision-balanced |
| Compatibility | Specifically designed for the LARCHOTEK Dolomiti 187 cm³ cylinder kit |
| Applications | High-performance street, touring, and sport engines |
Especially with historic wide-frame engines, installing a performance-oriented long-stroke crankshaft is a good opportunity to perform a complete inspection of the engine.
Many of these engines are now several decades old and have been opened, repaired, or modified multiple times over the course of their lives. The new crankshaft should therefore not be combined with worn bearings, damaged bearing seats, or aged seals.
The LARCHOTEK Passo Rolle Signature is the ideal crankshaft solution for a high-performance Dolomiti 187 wide-frame engine. A 60-mm long-stroke, the high-quality 115-mm race connecting rod, Ø15-mm piston pins, and precision balancing combine to form a package specifically designed for demanding street, touring, and sport engines.
Particularly noteworthy is the system concept: the crankshaft and cylinders were not selected independently of one another, but are matched in terms of stroke, connecting rod length, and engine character.
For those who want to do more than just install a Dolomiti 187—but rather build it into a technically sound and durable complete engine—the Passo Rolle Signature provides the ideal crankshaft base.
DE | €
