S p e c s: V9B1M motor

1978 - 1984
casing mouth: 2 transfer ports
induction: disc valve
bore: 49 mm
stroke: 51 mm
cubic capacity: 96.12 cc
compression ration: 8.75: 1
bhp at rpm: 3.1 @ 5200
con rod length:97mm
piston compression height: 36mm
piston type: domed
small end diameter:19mm
big end diameter:20mm

flywheel side bearing:
N204ECP (2 piece)
drive side bearing: 6303
clutch bearing: 16005
input shaft bearing: (flywheel side): 6200
output shaft bearing (flywheel side):

rear wheel bearing: 6204
flywheel side oil seal: 19x32x7
drive side oil seal: 22.7x47x7/7.5
rear hub oil seal: 27x37x7

Vespa 100 Sport links:
V9B1T electrical page
Engine Work
Casings: The crankcase mouth on this model was enlarged in 1966 to 61mm - an identical size as larger small frame motors like the 100 and Primavera. From 1963 to 1965 the crankcase mouth is only 56mm. See "kits" below for limitations because of the. The 16mm intake manifold is attached with only two studs compared to 3 studs on later PK models

Bearings: The flywheel side crank bearing is a two piece unit to making splitting the casings easier. This type of bearing can be used on other smallframes to replace the single flywheel bearing.

Crank: The crank is the same as the Vespa 90 and Primavera models up to the Primavera ET3. Any smallframe crank can be installed in this engine. Popular changes are to install a PKXL or PK125ETS crank which allows use of many different flywheels. Flywheel side bearings and seals will differ for these conversions.

Standard barrel: The original 100 barrel has three ports and can be used on the standard Vespa 100 or 90 models as the third port is completely contained within the barrel casting (i.e. no casing modifications are necessary. The barrel studs are short studs and pass only through the barrel base - the head is then bolted to the barrel. The Primavera ET3 barrel & piston can be used on this engine if the barrel studs are replaced with long ones to pass through the barrel to the head. Both the barrel and the piston will have to be replaced for this conversion.

Kits: Larger bore kits from Malossi and Polini (and others) will fit.

Ignition: The original 12V points can be replaced with a 12V electronic set up off a later Primavera ET3 or any of the PK range systems. Strangely, the 100 Sport flywheel is already set up for electronic ignition and only needs a stator and CDI change from a Primavera ET3 or other PK model.

Gearbox: Any smallframe gearbox will fit in the casings but almost all the parts will have to be replaced.