BGM PRO 177 Cylinder – Vespa 125–150 cm³ 2-Channel | Early Largeframe Models 1958–1979
Compatible with: Vespa Largeframe 125 and 150 2-channel models – VNB1-6, VNS1-6, VNC1T, VNL1-2, VBA1T, VBB1-2, VGLA-B, VLA1T
as well as transitional models GTR125 (VNL2T) up to 138956, Sprint150 (VLB1T) up to 105199, and
Super150 (VBC1T) up to 328128.
More torque for early Largeframe engines: The BGM PRO 177 is a modern aluminum cylinder
with a Nikasil coating for Vespa 125 and 150 cm³ models, featuring two overflow channels. The design combines early thrust,
a wide usable RPM range, and stable temperature control—ideal for everyday use, touring, and discreet, high-performance setups.
177 cm³ aluminum
Nikasil
2-channel engine block
Meteor piston
CNC cylinder head
Optional 187 cm³
BGM PRO 177 2-Channel in the video
Video about the BGM PRO 177 and its use on early Vespa large-frame engines with 2-channel engine cases.
Technical Highlights
| Cylinder material |
Aluminum, hard-coated Nikasil raceway |
| Design |
2-channel for early Vespa large-frame engine cases |
| Bore |
Ø63 mm |
| Stroke |
57–60 mm |
| Displacement |
177 cm³ at 57 mm stroke / 187 cm³ at 60 mm stroke |
| Piston |
Meteor, cast piston with high silicon content, two 1-mm piston rings |
| Cylinder head |
CNC-milled, tightly sealed combustion chamber, sensor thread |
| Applications |
Everyday use, touring, and tunable setups |
More torque for early 2-channel engines
Many early Vespa 125- and 150-cm³ large-frame engines have only two overflow channels. This version of the
BGM PRO 177 is designed specifically for these engine cases. This allows a modern aluminum cylinder to be used effectively even on older engine generations
without having to switch to a later 3-channel case.
The focus is not on peak power, but on torque that kicks in early and is widely usable. This is a perfect match for classic street scooters that are meant to be ridden with confidence in city traffic, on country roads, and on longer tours.
Why the 177 is so well-suited for touring
Early thrust: more usable torque even at moderate RPMs
Wide power band: less shifting and a more relaxed riding experience
Aluminum and Nikasil: excellent heat dissipation and stable temperature management
Suitable for box-style exhausts: pairs very well with unobtrusive touring exhaust systems
Upgradable: Later conversion to a 60 mm stroke and approximately 187 cm³ is possible
Aluminum cylinder with Nikasil liner
Aluminum transfers combustion heat to the cooling fins significantly faster than a traditional gray cast iron cylinder. The hard-coated
Nikasil bore surface serves as the actual sliding surface for the piston and piston rings.
This combination is particularly advantageous for touring: The engine quickly reaches a stable operating state and can effectively dissipate heat to the surroundings during
prolonged operation. Of course, this requires proper carburetion, ignition, and a compression edge.
Meteor Piston with Two 1-mm Rings
The BGM PRO 177 uses a Meteor piston with two narrow 1-mm piston rings. The design combines a field-proven
piston base with low ring mass and smooth operation in the Nikasil bearing surface.
New Meteor piston with Oil-Dot coating
The piston design has been further refined. A new feature is a dot-shaped Oil-Dot coating on the piston skirt, specifically in the piston’s guiding area.
Supporting the oil film: The dot-like structure forms small pockets that can hold lubricant.
Additional reserve: The coating supports lubrication at the contact surfaces of the piston skirt.
Cold start: The surface structure can help ensure smoother operation during the warm-up phase.
Normal operating conditions: Partial wear of the coating on stressed contact surfaces is possible during operation.
Practical Notes: Do not grind off the coating; break in the engine properly and adjust the fuel mixture, fuel injection, and ignition correctly.
CNC-milled cylinder head
The included cylinder head is CNC-milled and matched to the cylinder’s geometry. The correct squish edge is crucial for consistently smooth operation
It should always be actually measured during assembly and not determined solely by the nominal gasket thickness.
Practical values for the squish edge
57 mm stroke: in practice, approximately 0.8–1.2 mm
60 mm stroke: typically about 1.0–1.2 mm
Important: Always measure on an actual, assembled engine
With a 60 mm stroke, displacement is approximately 187 cm³
The cylinder can also be operated with a 60-mm crankshaft. A 63-mm bore and 60-mm stroke result in approximately
187 cm³. The additional stroke increases the displacement and simultaneously alters the valve timing.
During the conversion, the cylinder position, compression edge, and valve timing must therefore be rechecked and, if necessary, adjusted using appropriate gaskets or spacers.
Practical Tips from Scooter Center
Especially for early 2-channel engines
Jetting: Always adjust to match the carburetor, air filter, and exhaust.
Carburetor: The SI20 is roadworthy; with the SI20/20 or SI24, you can achieve a powerful touring setup very well.
Ignition: Points ignition only works if in perfect condition; an electronic ignition system generally requires less maintenance in everyday use.
Compression edge: Measure and adjust properly after assembly.
Gear ratio: The additional torque often allows for a longer overall gear ratio.
Exhaust: A good box-type exhaust system complements the cylinder’s early torque characteristics.
FAQ – Quick Explanation
The surest way is to count the overflow channels in the engine housing. For transitional models, the chassis numbers also provide a clue:
GTR125 through 138956, Sprint150 through 105199, and Super150 through 328128 belong to the 2-channel version relevant here.
In many cases, a functional touring setup is possible without extensive milling work. Those who want more power can specifically tune the intake and overflow ports. For a clean base setup, the jet settings, ignition, squish edge, and a suitable exhaust are particularly crucial.
For touring, a well-tuned SI20/20 or SI24 paired with a good box muffler is a very practical choice for everyday use. The key is tuning the entire setup.
Yes. A 60 mm stroke results in approximately 187 cm³. This changes the valve timing, and the compression edge must be readjusted. Depending on the configuration, appropriate gaskets or spacers are used.
Even with a modern piston ring groove and Oil-Dot coating, the piston rings, ring groove, and other engine components must run in smoothly with one another. A controlled break-in phase does not replace proper fuel injection and ignition settings, but it helps to thoroughly test the engine under real-world conditions.
Compatibility at a Glance
General rule: Compatible with Vespa 125 and 150 cm³ models with 2 overflow channels. For the GTR125, Sprint150, and Super150, there was a switch to a 3-channel system. For these models, the 2-channel version is only compatible up to the specified chassis numbers.
125 cm³ 2-channel
Vespa 125 T2 / VNB1-6 – 1959–1965
Vespa 125 S / VNS1-6 – 1959–1965
Vespa 125 Super / VNC1T – 1965–1969
Vespa 125 GT and Sprint / VNL1-2 – 1961–1973
Vespa 125 GTR / VNL2T: 2-channel up to chassis number 138956
150 cm³ 2-channel
Vespa 150 / VBA1T – 1958–1960
Vespa 150 / VBB1-2 – 1960–1967
Vespa 150 T4 / VGLA-B – 1959–1965
Vespa 150 GL / VLA1T – 1962–1964
Vespa 150 Sprint / VLB1T: 2-channel up to chassis number 105199
Vespa 150 Super / VBC1T: 2-channel up to chassis number 328128
Notes on Transition Models
Later chassis numbers often already feature a 3-channel engine housing.
Most reliable way to check: Count the overflow channels in the engine housing.
For 3-channel engine housings, please use the corresponding 3-channel version of the cylinder.
Conclusion
The BGM PRO 177 is the everyday-ready performance upgrade for early 2-channel large-frame engines:
more torque, a broad usable power band, and a modern aluminum cylinder with a Nikasil bore. With proper tuning, the result is a
smooth, powerful touring engine that also serves as a solid foundation for further upgrades, up to a 60 mm stroke and approximately 187 cm³.
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