[diametricalbenz]

The engine is not likely going to drop compression that much in 2 days and it was clear that the engine was running fine before he changed the fuel lines. There's likely air in the lines and it is just a pain to get it reprimed. I highly doubt the valves will become so tight that it will not fire unless the GP's aren't working, the fuel isn't gelled up and or the air is unusually cold.

Sako, are you getting some partial firing when it cranks or nothing at all? What's the air temp where you are?

Either way get the valves adjusted when you can.