177cc cylinder options for 2 and 3 ports Sprint engines

Some of our old beauties like the Sprint or GT 125 or even some Bajaj models have not many options for cylinders due to the small spigot sealing surface.

Our engine casings have not enough space at the side of the sealing surface so big cylinders like the Parmakit 177 or Polini 177cc won’t fit here. The result would be a dripping cylinder.

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.

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2 replies
  1. LasseDH says:

    Great post!
    I have the opposite problem. I have a 2 port engine, and a 3 port cylinder, where my spacer does not cover the port-hole in the cylinder 100%.
    Do you have any suggestions on how to solve it?
    It is a Vespa Sprint 150 2-port engine (1968) and a Polini 177 3-port cylinder

  2. Pelayo says:

    It’s simple. Block off the 3rd port. I used a DR177 3 port cylinder on my GrandTurismo 2 port case. The 3rd por simply doesn’t function. It runs well, and is fast. It loves high recs.

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