Modern Vespa

Hello everyone, I'm here because I'm trying to figure out why I'm getting a low compression reading of 81.25 psi. on my 1980 p200e.
I put new piston rings and honed the cylinder, also laped the head surface and cylinder surface as well but not seeing improvements. Any one can help please. thank you.

Moved to NSM.

did you seize it (and damage the bore) prior to the new rings?

Any chance you have pictures of the inside of the cylinder and the piston?

Any additional detail is helpful here, but as you already know, 81 PSI is under minimum compression.

Welcome to MV!

We're going to have a lot of questions, and our guidance will be as good as your answers.

Also, what's your overall level of skill as a mechanic, so we're all speaking at the same level.

Bore was worn and/or out-of-round. Honing will not fix that. OS piston and a re-bore or ( probably cheaper) new top end.

You can take your cylinder to a shop and have them measure the bore and tell you if it is within specs.

Could be an issue with the gauge. Have you tried using the same gauge on another scooter to see what it reads.

If it runs, the gauge is probably just reading low (maybe has a long hose, which can cause low readings due to the added volume of air). If it doesn't run, then the gauge is probably accurate.