S p e c s: VAM1M motor

1983 - 1986
casing mouth: 3 transfer ports
induction: reed valve
bore: 55 mm
stroke: 51 mm
cubic capacity: 121.17 cc
compression ration: 10.5: 1
bhp at rpm:
con rod length:
piston compression height:
piston type: domed
small end diameter:
big end diameter:

flywheel side bearing:10-7034
drive side bearing: 6303 C4
clutch bearing:
input shaft bearing: (flywheel side):
output shaft bearing (flywheel side):
rear wheel bearing:

flywheel side oil seal:20x35x6
drive side oil seal: 22.7x4705x7.5/7
rear hub oil seal: 30x40x7

Vespa PK125 Automatica links:
Service Manual
Parts Manual

Casings: The crankcase is shared with the PK 80 Automatica and is very unique to this range. One half of the crankcase bottom end can also have an oil metering device bolted to it that runs off a special geared nut on the end of the crank.

Bearings: The main bearing is shared with a typical small frame main bearing but the flywheel side is a needle roller type with an interior race that is fitted to the crank.

Crank: The crank is shared with the PK 80 Automatica. Not much tuning options as the bike is a reed valve intake as stock.

Piston: Totally unique....

Standard barrel: The standard barrel is surprisingly more modern than most Vespa motors. It is an aluminum barrel with a Nicasil pore and three large transfers from the casing mouth.

Kits: I don't know of any kits for this model.

Ignition: The 12V electronic ignition is similar to a Vespa PK type.

Gearbox: The PK 80 and PK125 Automatica differ from the PK50 Automatica due to the upper drive pulley. The lower drive pulley is identical on all three models.