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S p e c s: V9A1M motorinduction: disc valve bore: 47 mm stroke: 51 mm cubic capacity: 88.5 cc compression ration: 7.2: 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) flywheel side bearing: 6024 (1 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 90 links: Vespa 90 Overview Electrical Diagrams Parts Book Owner's Manual 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 and
the piston is different. See "kits" below for limitations because of
this. The 16mm intake manifold is attached with only two studs compared
to 3 studs on later PK models Bearings: Early motors had one piece bearings on both sides
of the crank which are a pain when splitting the casings. The one piece
flywheel side bearing can be replaced with a two piece to make
splitting the casings easier in the future. Use an SKF N204ECP for the conversion Crank: The crank is the same as the 100 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. Piston: On pre 1966 engines the pistons have a different wrist
pin set up using a 14mm pin and only a bronze bushing aat the small
end. Post 1966 engines have a 15mm wrist pin and a caged roller bearing
small end (see pic)
. Standard barrel: The original 90 barrel has only two opposing ports in
the barrel. The later 100 Sport or Primavera ET3 barrel & piston
has three ports and can be used on earlier models as the third port is
completely contained within the barrel casting (i.e. no casing
modifications are necessary. Both the barrel and the piston will have
to be replaced for this conversion. Kits: Larger bore kits from
Malossi and Polini (and others) can only fit on post 1966 engines
without enlarging the mouth to allow the barrel spigot to fit. Ignition: The original 6V points can be replaced with a 12V
electronic set up off a later Primavera ET3 or any of the PK range
systems. The flywheel and stator off an ET3 bolt right on, but many PK
flywheels use a different taper. Check here for a guide to smallframe
cranks. Gearbox: Any smallframe
gearbox will fit in the casings but almost all the parts will have to
be replaced. |
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Pistons
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