Modern Vespa

I pulled the head and cylinder from a Stella and found it pretty rusty. It had been sitting for a while likely outdoors. There were some vertical scoring marks more on the piston than the cylinder, apologies didn't get pics of that.

Nothing deep enough to catch a nail. Would an overcome be needed or could I get away with lightly honing the cylinder

Hone and reinspect it.

It seized at least once or twice (marks above the transfers and aluminum smear over the exhaust port), but maybe not irrecoverably.

I'm with Tierney: get the surface rust off, maybe some muriatic acid to remove the aluminum smear, then reinspect.

How bad is the piston?

I took some photos with my phone but they didn't save. Likely the power was too low. Anyway, the piston looked fairly close to this:

this is a photo I took off google image search of something comparable.



with much thinner rings.

the carbon on the top of the piston was very minimal, same with the head. there was this crusty buildup on the edges, looked like glue and I was concerned that i was molten metal, but it was just gunked carbon. it scraped off and brushed out with a little carb cleaner.

the wristpin was also fairly stiff. I hit it with some penetrant to loosen it up before putting it all back together.

Sounds like it needs a whole top end once over. Pull the cylinder and either overbore it with a 1st over piston and rings or get a whole new top end (for about the same price?)

Is that top ring upside down?

additional photos for reference

good call if it is. i would imagine the ring end gap would be signifiant.

The piston photo is not his, just representative. (and, yes, that ring is upside down)

If the piston crown was fairly clean, then that'd support the probability that it seized.

Is there scuffing on the sides of the piston or are the rings stuck in the channels?

Given it's a stock motor, you can most likely clean it all up with emery paper and get it running, ideally with new rings.

A bit of WD40 & 240grit should do the trick!

If it sounds like a Tractor, is blowing smoke out it's rattly exhaust & meandering along a quiet country road ... then it's likely to be a Tractor.
but ...
If it's piston sounds like a Tractor, is blowing smoke out it's rattly exhaust & just flew past a meandering Tractor that's going along a quiet country road... then it's likely to be Speedy!