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- Vespa Classic
- Spring for Primary - BGM PRO - Vespa PX, Cosa, T5 125cc, Rally, Sprint, VBB - 48 N/mm
BGM PRO reinforced primary spring with a spring rate of 48 N/mm for Vespa Largeframe. Higher spring force and greater usable travel than the original Piaggio spring. Ideal for overhauling the kick-start damping as well as for high-torque touring and tuned engines.
Compatible with: Vespa PX80–200, Cosa, T5, Rally, Sprint, and other Largeframe models with a compatible primary drive. Also suitable as a replacement spring for the BGM PRO repair kit BGM0195F48.
Greater spring force, more usable travel, and more reliable power transmission under high loads. The reinforced BGM PRO primary spring with 48 N/mm was developed for the shock absorption of classic Vespa large-frame engines. It combines a higher spring rate with a greater possible travel range compared to the original Piaggio spring.
Whether it’s a stock PX engine, a powerful 177 Tourer, or a high-performance PX200: The shock absorber must absorb high forces during every load cycle. The BGM PRO spring offers an alternative to the stock shock absorber spring that is designed for higher loads.
A two-stroke single-cylinder engine does not produce uniform torque. During combustion, the crankshaft assembly accelerates rapidly; between power strokes, the applied torque decreases again.
In addition, powerful load changes occur in the drivetrain during acceleration, shifting, and abrupt throttle release. These load peaks can be particularly pronounced in high-performance engines with a light flywheel mass.
This is where the primary drive’s shock absorption comes into play. The springs arranged between the primary drive components allow for limited relative rotation. In this way, short-term torque surges are elastically absorbed and distributed over time.
This reduces the immediate stress on the clutch, gears, and other transmission components. Especially in high-torque engines, effective shock absorption is therefore a crucial component of a reliable powertrain.
With a reinforced shock-absorbing spring, it is not just a matter of achieving the highest possible spring rate. The available spring travel is at least as important.
If a spring is fully compressed under load, its coils lie on top of one another. The spring can then no longer yield further and loses its elastic compensating function in this direction.
The result: Additional torque spikes are transmitted much more directly into the drivetrain. Among other things, this can place heavy strain on the clutch, primary drive, and transmission gears.
The BGM PRO spring therefore combines two key characteristics:
As a result, shock absorption remains within its intended elastic operating range for longer, even under higher loads.
The spring rate describes how much the required spring force increases as compression increases.
With a spring rate of 48 N/mm, an additional 48 newtons of force is required for every additional millimeter of spring travel. For an ideally linear spring characteristic curve, this corresponds, for example, to a force increase of 144 newtons with 3 mm of additional compression.
However, the spring rate alone does not describe either the preload or the maximum load capacity. The installed length, available spring travel, and the overall shock absorption design are also critical factors.
Modern large-frame engines achieve significantly higher torque values than the original Piaggio production engines. The demands on the entire powertrain increase particularly with larger touring cylinders, long-stroke crankshafts, and high-performance exhaust systems.
The BGM PRO spring is therefore not only suitable for a classic engine overhaul, but also for:
The reinforced spring supports robust kick-start damping, provided that the entire spring assembly and the primary drive are compatible with the respective engine configuration.
The BGM0190F48 is offered as a single replacement spring. It is suitable for replacing corresponding springs within a compatible primary drive or the BGM PRO primary repair kit BGM0195F48.
When performing a complete engine overhaul, we recommend inspecting all shock absorber springs for wear and tear and avoiding the combination of worn springs with new springs of a different design.
If you wish to replace the entire shock absorption system, we recommend using the BGM PRO Primary Repair Kit BGM0195F48. This kit contains the necessary springs as well as the appropriate repair components for a complete overhaul.
The BGM0190F48 is the standard 48 N/mm version for the corresponding Largeframe primary drives and the BGM PRO Repair Kit BGM0195F48.
The BGM0196F50, which is available separately, has a spring rate of 50 N/mm and a smaller inner diameter. The narrow additional inner springs for the 200-cm³ primary drives therefore do not fit into this 50-N/mm version.
Important: The two springs differ not only in their spring rate. The inner diameter, spring mount, and the intended combination with other springs are also critical factors in the selection.
A nominally higher spring rate therefore does not automatically mean that a spring is better suited for every primary drive.
| Feature | Version |
|---|---|
| Manufacturer | BGM PRO |
| Item Number | BGM0190F48 |
| Component | Primary Spring / Shock Absorber Spring |
| Version | Reinforced |
| Spring rate | 48 N/mm |
| Spring travel | Increased usable travel |
| Mounting dimension | Design true to the original |
| Application | Vespa Largeframe Primary Drive |
| Matching repair kit | BGM PRO BGM0195F48 |
| Contents | 1 spring |
For Vespa large-frame engines with the corresponding primary drive, including:
The actual fit depends on the installed primary drive and the intended spring configuration. For older vehicles and modified primary drives, we recommend comparing the springs with the existing ones.
To replace the shock absorber springs, open the primary drive. While doing so, inspect all shock absorber components for wear and damage.
Important: A reinforced spring does not replace damaged spring mounts, worn cover washers, or faulty riveting. Shock absorption must always be evaluated as a complete assembly.
Additional springs, cover washers, rivets, and other repair materials are available separately. For a complete overhaul, we recommend the BGM PRO Primary Repair Kit BGM0195F48.
It has a higher spring rate and a greater usable travel range compared to the original Piaggio spring. This allows the shock absorption to remain within its elastic operating range for longer, even under higher engine torque.
A spring can only absorb torque surges as long as it can still be compressed. Once its coils are fully pressed together, the spring travel is exhausted. A greater usable travel provides additional reserves before this condition is reached.
Yes. The BGM PRO 48 N/mm spring is also designed for high-torque large-frame engines. The key is to select a spring configuration that matches the specific primary drive design.
The BGM0190F48 has a spring rate of 48 N/mm and belongs to the standard BGM PRO Largeframe primary spring family. The BGM0196F50 has a spring rate of 50 N/mm but features a smaller inner diameter and cannot be combined with the narrow auxiliary inner springs of the 200-cm³ primary.
During a complete overhaul, it is recommended to replace them all at once. This ensures that worn or fatigued springs are replaced and that the spring set remains uniform.
