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BGM Tuning

BGM PRO Vespa 177/187 Cylinder Kit

BGM PRO Vespa 177/187 Cylinder Kit

Regular price £265.00 GBP
Regular price Sale price £265.00 GBP
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New version of the proven BGM177 cylinder for Vespa PX125/150, now also suitable for vehicles with electric starter.

Models this will fit:

LML 125 (2 stroke)
LML 125 Deluxe (2 stroke)
LML 125 DLX (2 stroke)
LML 125 Stella (2 stroke)
LML 150 Belladonna (2 stroke)
LML 150 Belladonna RV (2 stroke)
LML 150 DLX (2 stroke)
LML 150 Star (2 stroke)
LML 150 Via Toscana (2 stroke)
Vespa (Motovespa) Vespa 125 CL (engine 9CL)
Vespa (Motovespa) Vespa 150 CL (engine 9NC)
Vespa (Motovespa) PX 125 Iris (engine 99M)
Vespa (Motovespa) PX 150 Iris (engine 75M)
Vespa (Piaggio) Vespa 150 Sprint Veloce (VLB1T)
Vespa (Piaggio) Cosa 150 CL (VLR1T)
Vespa (Piaggio) Cosa 150 CLX (VLR1T300)
Vespa (Piaggio) Cosa 150 FL (VLR2T)
Vespa (Piaggio) P 150 X (VLX1T, -1980)
Vespa (Piaggio) PX 150 E FL (VLX1T, 1984-1997)
Vespa (Piaggio) PX 150 E (VLX1T, 1981-1983)
Vespa (Piaggio) Vespa 125 TS (VNL3T)
Vespa (Piaggio) Cosa 125 CL (VNR1T)
Vespa (Piaggio) Cosa 125 CLX (VNR1T300)
Vespa (Piaggio) Cosa 125 CLX (VNR1T301)
Vespa (Piaggio) P 125 X (VNX1T, -1983)
Vespa (Piaggio) PX 125 E FL (ZAPM09300, 1998-2000)
Vespa (Piaggio) PX 125 E FL (ZAPM09302, 2001-)
Vespa (Piaggio) PX 150 E FL (ZAPM09400, 1998-2000)
Vespa (Piaggio) PX 150 E FL (ZAPM09401, 2001-)



The BGM177 cylinder is a very powerful, durable and fully everyday conversion cylinder. It covers a very wide range of applications. By simply swapping the cylinder, you can more than double the power of the 125cc stock engine and surf the big torque wave with ease. Likewise, the exact same cylinder can turn the engine into a beast with over 20hp if it finds the right environment (carburetor, exhaust, crankshaft). Thus, the cylinder offers beginners a perfect basis to be able to expand this, as needed, more and more.

The BGM PRO 177 replaces the original cylinder, the conversion is simple and easy to revise if necessary. With its large displacement of 177ccm, the BGM PRO 177 always offers a confident and relaxed riding experience. The engine rides as powerful as a 200cc machine, but with exactly the same reliability and durability. It achieves this by operating in the same rev range as a standard engine. Low fuel consumption and the associated high range are another bonus of the BGM PRO 177 cylinder. The cylinder is designed to be fully compatible with all stock components. The only adjustment made is a change in carburetor jetting and a spark plug with adjusted heat value.

The BGM PRO 177 cylinder is a hard ceramic coated aluminium cylinder with 63mm bore. The coating (nickel silicon carbide) provides an extremely hard and durable race. The piston has a high silicon content. This means it has less thermal expansion, is more wear resistant and thermally very stable. Two 1mm thick piston rings minimize friction, increasing performance and speed stability.

  • Cylinder material: aluminium

  • Raceway: coated with nickel-silicon-carbide

  • Bore: Ø 63mm

  • Displacement 57/60mm Stroke: 177/187 cc

  • Piston: cast piston with high silicon content and two 1mm steel piston rings

  • Recommended pinch point: 0,8- 1,2mm

The cylinder head is CNC machined from the solid. The combustion chamber is countersunk 4 mm deep into the cylinder for perfect centering. This also makes it much easier to adjust the squeeze edge and the seal is always guaranteed. There is a thread in the middle for mounting a temperature sensor. The compression ratio was deliberately chosen low and is 10.3:1. For this reason, the squish edge can be lower than with comparable other cylinders.

The cylinder kit is designed as a plug 'n play solution. The cylinder offers, with full reliability, however, still a lot of potential upwards. With a 24mm carburettor of the 200cc models and a BGM Big Box Touring exhaust the power is already around 15hp and the torque around 17 - 19Nm at the rear wheel. The BGM PRO 177 responds very gratefully to all performance-enhancing measures such as:

  • A bigger carburettor (BGM PRO Faster Flow SI24 (BGM8570))

  • Crankshafts with extended intake timing (BGM031120G) and/or more stroke (BGM031121G)

  • An optimized pole wheel (BGM8025RT)

  • Optimization of the intake tract (milling of the intake port)

  • Enlargement of the overflow channel surfaces in the cylinder base sealing surface as well as in the motor housing (The overflow channels at the cylinder base have a gate. This makes the channels on the cylinder the same as those on the engine case. The sprue can be easily removed to use the complete cross-section of the channels).

The cylinder is factory prepared to be used with a crankshaft with a larger stroke (60mm instead of 57mm as standard). This increases the displacement to a whopping 187ccm and the power determining timing angles of the channels are increased. With appropriate crankshafts and further modifications to the engine, the cylinder can also be used with an even larger stroke (up to 64mm, see KINGWELLE crankshafts) without any problems. With this it reaches the full 200cc, but needs an intake control via a diaphragm intake (e.g. from MRP Racing 3331680 or 3331682) due to the necessary crankshaft.

The BGM PRO 177 cylinder is already very efficient and powerful due to the optimized CNC cylinder head with a tightly toleranced squish edge. The very high quality ignition components ex works on Vespa PX models up to 2011 are therefore ideal for continuous operation. Special ignition modules or a variable ignition adjustment are therefore not necessary for high performance and reliability. A simple static ignition setting of 19° from TDC is recommended, but the cylinder can easily be operated with the 18° pre-ignition as factory set on the PX125E models. Models from 2011 onwards use ignition components from China which do not allow very high revs. Here can be converted by replacing the ignition base plate, the pole wheel and the CDI to the old, better construction. We also offer a complete set (BGM666PXL). However, with this set the possibility of using an electric starter is omitted (the pole wheel has no ring gear for the electric starter).


  • 57mm stroke: overcurrent 118°, exhaust 171° (with foot seal 0.2mm, no head seal)

  • 60mm stroke: overflow 123°, exhaust 173° (with foot seal 0.2mm, head spacer 1.5mm)

  • (head spacer for 60mm stroke not included, optionally available, see accessories)

Many customers extend the gear ratio already in low power stages in order to be able to use the newly gained power of the engine even better. This is done by simply replacing the clutch pinion. This is relatively easy to achieve after removing the rear wheel and the clutch cover behind it. Alternatively, it is also possible to change directly to a reinforced clutch type (see accessories). After that, the gears can be accelerated significantly further and the achievable top speed is increased. The engine has so much power that the acceleration is usually better because you don't have to shift as much or as fast.

Generally the gear reduction can be longer than usual in the 177cc class because of the high torque. If you use a touring oriented exhaust with early support (BigBox Touring, Polini Original Box) you should use at least a clutch pinion with 23 teeth on a PX125. We carry these especially for the original primary wheel with 68 teeth (see accessories). Engines with long stroke shaft will also easily pull a 24/65 reduction on PX125 gearboxes.

Universal plug 'n play cylinder kit with early onset of power, wide rpm range, reliability like an original cylinder, low fuel consumption and therefore an unbeatable price/performance ratio!

    performance class: sport
    Gudgeon pins
    diameter: 15 mm
    Spark plugs
    thread type: M14x1,25
    thread spark plug: long
    heat rating NGK: B9ES
    displacement: 177 cm³
    bore: 63 mm
    engine type: 2-stroke
    type of cooling: air cooled
    material: aluminium
    material piston cylinder surface: Ceramic
    cylinder head inclusive:
    cylinder gasket set inclusive:
    number of transfers (incl.boost ports): 6
    number of boost ports: 2
    shape exhaust port: single port (oval)
    exhaust mounting: stub
    diameter exhaust stub: 37 mm
    number of piston rings: 2
    production method piston: cast
    Piston rings
    piston ring type: common ring
    circlip type: C-type
    wire size of circlip: 1,0mm
    Cylinder heads
    cylinder head type: one piece
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