an engine sitting for a year with the piston rings in the same spot doesn't do any good for them. Same with the valves - especially with the rocker cover off in that time - valve stems could have a coating of surface rust on them which wont be nice when they go up and down the guides. I would say piston rings and sealing valves would be affecting the compression.
If that fails just go out and buy some a can of compression, should sort it out.
agreed, these engines are pretty sturdy but i think even if you do get it running its guna destroy itself pretty quick ay, but good on ya for trying