I had picked up a "running" 2005 PX150 and started trying to sort it out. After running into some fuel issues I peaked inside the tank and saw more rust than a coastal farm. It was far worse when I pulled the tank. There was like a gritty sandy material inside. It was bizarre. I once did a rebuild on a 72 primavera that sat for 30 years in a kwanzza hut and that tank was gorgeous by comparison.
Consensus is that the muck and grit was ethanol residue. . I guess it absolutely is worth looking for straight gas without corn in it.
Anyway... Threw in an aftermarket tank and went about rebuilding the Spaco carb. Worked OK but died after a few miles and would overflow the float chamber pretty fast.
Went back and rebuilt the carb a second time... Soaked in a carb cleaner bath for 24 hours, blew out with air.
Same result. After about a mile carb clogged and fuel starved engine dies.
Mrrrph.... so I had an old original 79 Dellorto 20/20 from P200 (I had upgraded to a 24/24 on the P200 in like 2008.) Cleaned it up and threw it in the pX150 and it is running like a scalded cat.. well almost.
Seems like it will only run with the petcock flipped to reserve? Any thoughts other than pulling the tank and noodling with the tap? BTW I tested the new tank for flow and leaks it before dropping into the scoot and fuel flowed in the "on" position". (Maybe just not enough. )