RD BGM Vespa 177 Cylinder Carburettor Jetting Kit (SI 20.15-17 A-D/20.20-26.26E/G/H)

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Ron Daley MotorcyclesPRODUCT CODE: RDBGMJ000KT
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RD BGM Vespa 177 Cylinder Carburettor Jetting Kit (SI 20.15-17 A-D/20.20-26.26E)

The BGM177 is an easy cylinder to tune due to its linear power development. It gives a clear feedback if the engine is running too lean or too rich. This kit contains jets to ensure a clean basic tuning of the engine with a SI stock carburrettor.

The tuning set refers to a conventionally built engine with BGM177/187 and so-called box exhaust system. Due to their perfectly matching cylinder characteristics we recommend the BGM BigBox Touring or the Polini Box. With their harmonious torque curve, the engine can be tuned quickly and easily. It does not require any dynamic ignition adjustment or other special processing of the carburettor. In general, however, you should take a few hours for a good basic tuning of the engine.

The engine's jetting requirements are heavily dependent on the air filter used. The stock air filter doesn't look like much of a performer, but it is not a throttle. So there is no need to replace it with a funnel, venturi or even omit it altogether. The SI carb is very sensitive to changes in/on the air filter, so it should be kept and not modified for a good basic setup. The bottom of the air filter has a heart shaped cutout. This sits over the jets of the carburetor when installed. It is often recommended that this be drilled out or even removed altogether. This has a great influence on the mixture formation and can quickly lead to a dangerous lean. Changes should not be made in this area at the beginning.


  • Main air correction jet: 160
  • Mixing tube: BE3
  • Hauptdüsenset: 115-118-120-122-125-128-130-132-135-138
  • Auxiliary nozzle: 55/160

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