Gearboxes from BGM Pro for Vespa large frame engines. Available with or without main shaft. For highest demands the gears are made of high-alloyed NiCrMo case hardening steel (20NiCrMo2-2/ AISI8620). This extremely good base material withstands even the highest engine power. The precisely defined surface hardening to 58-60HRC makes the sprockets permanently resistant to wear. This makes the BGM gear parts an uncompromising material for every serious engine builder.
USE
The highly developed gear parts can be used for all types of stress, no matter if standard engine, tourer or racer. We offer the gearboxes in the gradation of the PX125 (short fourth) or the PX200 (original gradation). Both versions are compatible with the auxiliary shaft of the 125-200cc models. Sporty engine/driver use the option with short fourth gear. The gear step is then less large and the engine immediately reconnects to the power band.
PASSEND
The gearboxes of the Vespa Largeframe are roughly divided into old and new type:
PX old (-1983)
The old type was used until about 1983. It uses a main shaft where the gears are held by a snap ring only on one side (Lima). In addition, it has a cranked shifting cross. PX Disc, My, 2011, T5, Cosa
The new type has been used since about 1984, not only in the Vespa PX but also in the T5, Cosa and its derivatives such as LML Star 2Takt and Stella 2Takt. The so-called Lusso transmission has two circlips on the main shaft, the shifting cross is flat. This type is considered to be more stable than the old one, because the bearing surface in the middle segment is wider and the main shaft is segmented, thus fixing the gear shifting cross under load. The Lusso gearbox is recommended for engines from 25PS upwards.
SPECIAL CASES
PX80, VNA, VNB, VBA, VBB, Super, GL, Sprint, GT, GTR, TS, Rally
The PX80 engines as well as their predecessors (mostly still original with contact ignition) use their own transmission gears. However, these can be exchanged without problems against the ones offered here. The simultaneous exchange of the layshaft / auxiliary shaft is then also necessary. Otherwise the gear teeth of the gear parts do not match. The motor housing may have to be adapted to the larger seat diameter of the auxiliary shaft. It is often sufficient to remove the bushes in the motor housing at the auxiliary shaft support (PX80) or to use a suitable auxiliary shaft.
To identify loose gears, simply measure the middle section:
The middle section on which the gear cross rests is old at
- PX (until 1984, cranked gear cross): 5mm
- Lusso (from 1984, flat gear cross): 6,5mm
The middle segment of the BGM gangwheels is larger (approx. 1/10mm) and thus offers even more contact surface for the gear cross.
The gang wheels have a marking (TOP) for installation direction. This should look in the direction of the gear shift lever when installed. The installation clearance between the gearwheels and the shoulder ring should be determined with a feeler gauge and adjusted to approx. 0.15-0.35mm.
TIP: The gear shift bolt has a left-hand thread. Therefore loosen it by turning it clockwise.
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