Carburetor tuning kit BGM177 Dell'Orto SI20/20D, SI24/24E, SI24/24H, SI26

CARBURETTOR TUNING KIT BGM177 FOR DELL`ORTO SI20/20D, SI24/24E, SI24/24H, SI26 WITH STOCK AIR FILTER

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

The tuning set is intended for a conventionally built engine with BGM177/187 and a 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. No dynamic ignition adjustment or other special carburettor processing is required. In general, however, you should allow a few hours for good basic engine tuning.

SUPPLY

• Main air correction jet: 160

• Mixing tube: BE3

• Main jet set: 115-118-120-122-125-128-130-132-135-138

• Auxiliary jet: 55/160

The jet set is based on the basic jetting of the SI24/24E carburettor on PX200 models. The jetting is already very close to ideal for a good-running engine and only needs a slight upward correction in the main jet area (larger main jet). Anyone using an SI24 carburettor on the BGM177 therefore generally already has a very good basic setup and only needs a main jet set (exception: carburettors from German PX200 models with a 10PS cylinder. A 190/BE4 air correction/mixing tube combination was used ex works. Please replace these with the components included in the set). The BGM Faster Flow carburettors with 24/26mm also use the good basic setup of the PX200 models with 12hp.

AIR FILTER
The engine`s jetting requirements depend heavily on the air filter used. The stock air filter may not look like much of a performer, but it is not a restriction. There is therefore no need to replace it with a funnel, venturi or even omit it altogether. The SI carburettor is very sensitive to changes in/on the air filter, so it should be retained and not modified for a good basic setup. The bottom of the air filter has a heart-shaped cutout. When installed, this sits over the carburettor jets. It is often recommended that this be drilled out or even removed altogether. This has a major influence on mixture formation and can quickly lead to a dangerously lean mixture. Changes should not be made in this area at the beginning.

Note: There are stock air filters that already have two holes (Ø6+Ø8mm) ex works. These filters originate from Vespa Cosa models, which have a second air filter and therefore completely different requirements for mixture formation. If possible, replace this filter with the closed type used on PX models.