Modern Vespa

Question for the smallframe specialists.

I have an early V90 that I'm refurbishing from the crankcase out. The swingarm bushings and shock mount bushing were toast, so I've pulled then to replace them.

Most of the parts sites list smallframes as having the same size bushing on both sides of the swingarm, but this bike has a larger one on the fan side of the motor, like my P series.

Which are the proper bushings for early smallframes?

I did find my answer. To tie this one up for the next person, here's a solution.

I didn't look hard enough. Most smallframes do use the same size swingarm bushings. However, digging into parts diagrams revealed that the early V9A uses the same bushings as the VNA/VNB/VBA/VBB largeframe models of the early sixties.

Add another line item to variance list between pre- and post-'66 smallframes.

Thanks. Good to know ...'64V90 project in line...

watching with interest, new to me 1964 90 as well.

"Add another line item to variance list between pre- and post-'66 smallframes."

I'd be interested in such a list. I had a '76 that I sold recently but I haven't really gotten far enough into the '64 to compare.

Moto64
Here is what I have learned so far.
63 thru 65
Small engine door
56mm spigot opening VS 61mm on '66 up
Bushing in small end of rod vs needle bearings on '66 up
The four bolt wheel models have a 1 piece front axle vs the two piece axle on 5 lug wheel models.
Early models call for headlight part 70550 (may fit later models)
Early motor cases can be cut to 61mm and have the later crank added.
Then you can use later barrel kits. Will require changing engine shroud and as I understand it, it's a pain to change the plug with the small door.

Thanks

Good list. Here's a few more items:

Smaller cooling fins on the cylinder barrel. Cooling shroud is metal and only fits the early bikes (maybe the 50s too?)

Smaller fan shroud with a different bolt pattern. Not certain, but I believe the cooling fan is a bit different too.

Rear brake plate has a different hole spacing. Plate and gasket are specific to early bikes.

Flywheel side of the driveshaft rides on an oil-grooved bushing instead of a roller bearing like later bikes. I believe the bearing is a different diameter, so late axles probably don't fit.

On the crank/piston relationship...the piston pin diameter is different too. Can't interchange early and late V9A pistons easily as the spacing between the piston pin bores is narrower on early pistons, in addition to having a 1mm larger pin bore.

The rotary pad duration on early V9A cranks is 101 degrees. Later cranks have a 110 degree duration. The Mazzuchelli replacement crank for early V9As has a 110 degree duration; maybe a touch more breathing at higher RPM?

Early V9As have a different clutch actuator pin than later models. It has one leg on it rather than two. Not sure if clutch covers interchange.

I'm sure I'll remember more later, but the takeaway is that Piaggio made a lot of changes between the early and late motors.

Chassis wise, I'd also mention that the early bikes had a smaller fuel tank and a larger tool bucket than the '66-on smallframes.