Allen joined me at the hangar and we located the idle mixture screws underneath each carburetor. The instructions say to close the screw all the way in and then one and a half turns out. Turns out that’s how they were set.
So, with the cowling off, I pushed the plane out for another idle speed test. The plane didn’t want to start again and when it finally did I was treated to the same violent shaking again. After a short while I was aware of being hit with splatters of fuel so I quickly shut the engine down.
A look at the engine compartment showed both float valve overflow lines were full of fuel, and Allen confirmed that’s where the fuel had been coming out from.
So I pushed the plane back in and set off for some online research. Everything was good before the airport closure, it was starting up and running just fine. What had happened during that time?