Some of our old beauties like the Vespa Sprint or GT 125 or even some Bajaj models have not many options for cylinders due to the small spigot sealing surface.
This picture shows a spacer for the 177cc Polini cylinder. You can tell that the ports are not matching at all and that the casings are just too small.
In the picture above you cann see a spacer for the Pinasco 177cc alloy cylinder made for engines with 3 ports. Pinasco cylinders are known for their quality and reliability. The spacer looks like it would fit but there would be less than 1mm sealing surface at the sides which is again way too less for proper use.
This upper picture shows the Pinasco 177cc alloy cylinder made for 2 port engines. The spigot has been reduced by the size of the spacer. The spacer itself covers the 3rd port and parts of the 2 side ones in order to make it usable for 2 port engines. This option would kill 2 birds with one stone. You could use the reliable Pinasco alloy cylinder and you could also cut out the 3rd port for our casings.
The best matching alternative is the DR 177cc cylinder. As you can see the sealing surface fits perfectly as the DR is close to the original one. This cylinder is also the cheapest one out of the 177cc cylinders.
There is of course also an alternative for the Vespa freaks. It would be possible to use a crankshaft of the PX200 which has a rod of 110mm (5mm longer than the original one). A spacer with a height of 5mm would adjust it again and you could port the spacer instead of the casings and then all variants of the 177cc range would be possible to use. But keep in mind that the flywheel and the stator plate need to be exchanged in this case as well.
This post is also available in: Deutsch