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 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 carburetor.

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.

SUPPLY

• Main air correction jet: 160

• Mixing tube: BE3

• Hauptdüsenset: 115-118-120-122-125-128-130-132-135-138

• Auxiliary nozzle: 55/160

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

AIR FILTER
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.

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