Oh well Gaseous, if you can admit to a Puch Maxi, I will admit to a Norton Villiers Triumph Easy Rider (NVT ER2P) step thru' moped. The frame was the petrol tank and you add to add your two-stroke oil into the tank from sachets.
NVT ER2P
But I know someone who had an even more embarassing moped but my lips are sealed
Cheers
Whirls