273, could it be a commando and CAM question?

I couldn't look through the plug hole on mine but didn't try that hard. Didn't know till I
pulled the head and saw the flat piston. Think if you go out to the Egge website that still sells 273 HP pistons you can see a picture of the regular and high compression pistons. Got a feeling that whoever rebuilt your motor did it right and put the good pistons in it for you. By the way - what's regular gas going for over there a gallon?
Ours is in the $3.8xs now.

I'll try the Egge website!

One liter of 98 octane gas is 16.33 sek (in Stockholm) and 2.45 usd if google calculated right for me. It's very expensive now.