WHY
Shoulder rings are used to compensate for the axial play between the gears. Spacing out the gears is essential for clean gear shifting. The tighter the clearance is selected, the less the gears can slip sideways. The gear change is more precise as the gearshift cross now engages exactly in the middle of the gearwheel and does not push it away first. It is therefore worth measuring the gearbox precisely.
HOW MUCH
The play specified by Piaggio is 0.15-0.40 mm. It is determined using a feeler gauge between the gear wheel and shoulder ring.
DISPECTS
There are two original versions of the shoulder rings:
- Thick (2.0-2.5mm original with only one lug) suitable for Vespa Largeframe from 1952-1984
- Thin (0.9-1,4mm with four lugs) suitable for Vespa Smallframe and Vespa Largeframe from 1984 (main shaft with two shoulder rings/sear rings)
OLDIES
The thick version of the shoulder rings for Largeframe Vespas before 1984 has not been available from Piaggio for some time. Thanks to bgm PRO, the matching shoulder rings in the 2mm to 2.50mm range are now finally available again for these transmissions.
As a deviation from the original, they have 4 lugs for locking, as with the more stable Vespa PX Lusso variant. It is therefore no longer possible to knock off the individual lugs in the new design.
TIP: The exact determination of the play between the gearwheels is only possible with a feeler gauge (see accessories). Don't forget a new BGM Pro gear cross and the transmission oil.
