Modern Vespa

Hi everyone,

I would appreciate some advice. I bought a Malossi overdrive gear kit for my 2012 GTS, and had the gears pressed by my local shop. All went smoothly with the intermediate gear (pink arrow). However, the axle was deformed when the driven gear (blue arrow) was installed. I noticed this when the end of the axle shaft would not slide into the bearing assembly (red arrow).

A measurement of the (~1/2" long) portion of the shaft assembly that sits in the bearing assembly (red arrow) showed that it was in spec at the base, and for approximately 75% of the shaft length. The last 1/8" at the tip was mushroomed, measuring at most 9/1000" out of spec.

I assume the gear wasn't perfectly aligned when it was pressed on and that it bound before dropping in place. It was installed with a press, not a hammer (I trust my mechanics and they told me they pressed it- also, no tooling marks).

I sanded the tip by hand and removed the 9/1000" to a 1500 grit polish, until it was as close to spec as I could get (measuring +- 3/1000") and it fit in the bearing with the same feel as the other shafts (maybe a hair looser).

No vibrations or sounds on a test ride.

The service manual doesn't list acceptable tolerances for the axle.

So, I ask, are these tolerances material? Should I run it, or replace the axle?

Thanks for your help!

You're likely good to go. I've encountered this when pressing gears before. Usually, I'll use press plates with a hole for the boss to pass through or some gear kits include pressing tools to avoid deforming the shaft.

I'll resort to a spring pass in a lathe if it's really noticable, but usually just spinning the shaft and dressing it with a strip of crocus cloth is sufficient.

Thank you!