That is to funny that you would bring that up, I was flying the cub yesterday and the right piston wouldnt stay running. Then I could even get it to start. This is on the 90TS.
After screwing around and checking glow plugs, Pulled the valve cover and found one of the push rods was not opening the valve . Put it back on the back side of the valve rocker, but would stay there.

The engine only has 3 flights on it. So I am going to send back to Horizon for repair.
Not sure what happen?????