Gents

Today we were early at the field. My friend Roberto was going to fly. His PA 61 wouldn't start...
It did start after a lot of flipping, priming, plug removing... To fly a few laps, enter mach speed and quit due to overheating.
The ship was perfect las weekend.
Then me. First flight the ST 51 was OK, though sped up a little at the end of the run. Second flight, a couple laps and enters mach speed, keeping that way till the end of the flight. Then, it wouldn't work... It started, but the needle was useless, it seemed to be chocking, no matter what. Checked everything, even replaced plug and fuel filter, the same thing. The ship was flown last Tuesday, perfect runs.
Then, Marlus arrived, but didn't take his ship out of the car (the wind was that bad today...) and he tells me yesterday, his RoJett 76 misteriously had similar issues during a flight, entering a rich 4 cycle that barely kept the ship airborne...
One thing I noticed is that the fuel was kind of bleedind from the uniflow vent, it was like the engine couldn't suck the fuel....
I'm totally clueless with what the fu@# has happened...
Help, please...
Around 80/90ºF today, turbulence, crazy weather, high humidity....should have stayed home....

Marcus