Four strokes are much better at fuel draw than the current two strokes with their big carb throats. So yes, a four stroke will run quite adequately with no tank pressure, but I treat tank pressure as a plus to the over all fuel system. For instance in a long upward climb the pressure will ensure better performance. YS is a different matter since it has its own pressure feed system. I am told Laser engines do not even have a pressure tap on the exhaust system for their engines.

I had a pressure line pop off the other day. My Magnum did not even miss a beat, never slowed down, kept right on going. In my case the very end of the tubing split. I replaced it anyway. I love the old lady, she just keeps on chugging along. Looking a little worse for wear but turns the prop with authority.

Cheers,

Chip