Problem solved. After replacing the carburetor to a plastic carburetor there were no more vapor lock issues. The carburetor's temperature didn't pass 105 Degrees F with an engine temp of 225 F.

Yeah... right... The whole world is using metal carburators so that is the problem.....

I'd be wondering what made the metal carb get hot enough to boil fuel.

Cool story I guess...

as the Mephisto came with a plastic Carb...

HIS Mephisto came with an aluminum carb. He already said that earlier in the thread.

Probably the body shell was redirecting air around the base of the engine so the carburetor wasn't getting blasted with direct high-speed airflow. Some people might choose to blame it on the user, but people who actually design engines clearly think otherwise. It's not like he's the first person to have problems with an aluminum carburetor overheating. There's a reason why even high-end engine manufacturers are switching to composite carburetors, and why O.S. started equipping the mounting collars of their aluminum carburetors with composite insulators a long time ago.

I first would have taken the carburator apart. Check is all the O-rings are there and not damaged and if there is a metal chip somewhere inside.
Last I did read somewhere that a guy with issues did find out there was no O-ring on the main needle....

As mentioned there are plenty of engines running with an aluminum carb so it is no standard error.