Modern Vespa

2015 PX125 thus with cat and with mix pump.
Done just 5k kms.

We went on an all in all 150 km route with no issues. Well almost none. The mix oil started to leak from the fuel tap. Not sure if that is of importance for the later issue.

After lunch again running ok on the way home. We stopped at a road side café.
After this break the engine was seize rock solid. Period.
Kick starter moves freely with clutch pulled in. Scoot roll freely with clutch pulled in.
All solid with clutch engaged.

Still plenty of oil in the tank. Sight glass full.

Have the scoot at my place now.

Suggestions? Can the fuel tap have impeded oil flow??? or is the oil tank 'tap' always open and thus a leak equalling less gravity feed to the pump thus engine?

¿Qué?

The oil goes from the oil tank to the carb via a separate line, then is dumped on top of the crank via a separate channel that merges with the fuel/air mixture right above the carb slide. Not sure what oil you could find leaking at the fuel tap.

Maybe check if the oil line disconnected from the oil pump where it slides onto the tube in front of the carb box. If not that, check the line where it connects to the oil tank. None of these are probable, but anything's possible I guess.

My bet is that it's not the oil pump, as it is a very reliable piece of kit that wouldn't fail in 11 years if it hasn't been messed with.

You could seize with an air leak, an overly hot plug, or a variety of other ressons maybe related with the cat set-up, which I'm fortunate enough not to be familiar with . What I find strange is that it seems it was running fine until you parked it, then it seized while you were day-drinking. Not a common occurrence.

My guess
Something in the barrel not right... piston circlip stuck in the cylinder?

Same here; baffles me.
If anything cooling down should fréé it up.

The plan was to replace the cat pipe with a 'standard'one. Clueless about the jetting but obviously have a look at that too.

Yes, checking the oil lines. There was no issue with the connection to the pump so was planning to lift the tank unit.

Now the agenda has the acute problem on top of the list.