GTR engine upgrade


This is my first post so go easy on me!

I have a 1971 Vespa 125 GTR with everything original except for a 12v conversion. I am going to be using the scooter for commuting and touring so am looking to increase the power. I am tempted by the Polini 177 cylinder kit, is it reasonably easy to fit? Also not sure what carb to fit with it? Would I also need to change the crankshaft, if so what is a good reasonably priced one?

I am going to buy a new exhaust and am thinking of getting the Sito PLUS will this work well with the Polini kit?

Any advice gratefully received.




Hi Dave


My recommendation for you is the following setup


Pollini 177 Cylinder Kit

24 SI Carburetor (from the PX200)

Sito Plus or SIPT5 exhaust.

Racing Crankshaft from Mazzuchelli


Please watch out for 2 thing:

1. The measure of your crank bearing because there were differences in the seventies.


2. Check if you have 2 or 3 boostports.





Thanks. I would not have check the Crank bearings and the boostports so you have possibly saved me a load of grief!



You´re welcome dude !