BGM PRO 177cc cylinder for Vespa Largeframe 2-port engines
✅ Performance plus suitable for everyday use
The BGM177 cylinder is a very powerful, durable conversion cylinder that is fully suitable for everyday use. It covers a wide range of possible applications. The power of a 125cc standard engine can be more than doubled simply by replacing the cylinder.
In the version for Vespa Largeframe engines with 2 overcurrent channels, a 2 mm thick base gasket is used. The cylinder is prepared for this.
✅ Plug & play replacement for the original cylinder
✅ Power like a 200cc engine with the same reliability
✅ Low consumption and long range
Compatible with all standard components. Only the jetting and spark plug should be adapted. Older SI20/17 carburetors should be replaced by SI20/20 with long air filter.
Features
- Aluminum cylinder, hard-coated (nickel-silicon carbide)
- 63 mm bore
- Displacement with 57/60 mm stroke: 177/187 ccm
- Cast piston with high silicon content
- Two 1 mm steel piston rings
- Recommended crushing edge with 57 mm stroke: 0.8-1.2 mm
- Recommended crushing edge for 60 mm stroke: 1.0-1.2 mm
✅ Cylinder head
CNC-milled from the solid. The combustion chamber is recessed 4 mm into the cylinder, which simplifies the squish edge adjustment and ensures perfect sealing. Also prepared for temperature sensor. Compression ratio: 10.3:1.
✅ Further tuning
With 24 mm carburetor + BGM BigBox Touring, approx. 15 hp and 17-19 Nm are already available.
Performance-enhancing measures:
- Suitable exhaust system (e.g. BGM BigBox Touring, Polini Box)
- Larger carburetor (e.g. BGM PRO Faster Flow SI24)
- Long-stroke crankshaft with extended intake angle
- Electronic ignition (e.g. BGM666SP1)
- Machining of intake duct/rotary slide valve
- Enlargement of the overflow channels in the housing and cylinder base
✅ More displacement and power
Prepared ex works for 60 mm stroke: 187cc total displacement. Control angles increase as a result.
Recommended head gasket: 2 mm (optionally available).
✅ Ignition
Contact ignition can still be used, but should be in very good condition. Better: Maintenance-free electronic ignition. Recommended setting: static 19° from TDC.
✅ Control angle
- 57 mm stroke: overcurrent 118°, exhaust 171° (with 0.2 mm base gasket / 0.5 mm head gasket)
- 60 mm stroke: overflow 123°, outlet 173° (with 0.2 mm base gasket / 2 mm head gasket)
Head gasket for 60 mm stroke not included - see accessories.
✅ Gearbox
Many extend the transmission ratio at an early stage by replacing the clutch pinion (e.g. 23/65 or 24/65). Alternatively: Install a directly reinforced clutch. Recommendation:
- Vespa Sprint (10") with touring-oriented exhaust: at least 23 teeth
- PX125 gearbox with long stroke: 24/65 can also be ridden without problems
- 8" tires: e.g. 24/64 possible
Conclusion
A versatile plug & play cylinder kit with early onset power, a wide usable rev range, very high reliability, low consumption - and an excellent price-performance ratio.
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