Yes, this one. Its not very new, the engine has had nearly 2L through it. I have stripped it quite a few times in the past, sealing everything up properly apart from the moving parts.
And if you take the carb off and look down the hole, you can see the crankshaft, which opens up on the upward stroke. Then it closes and the piston goes down, and the pressure escapes around that opening on the crankshaft (which is facing down at this moment) and around the wall which holds it, up into the carb hole.