The moped doesn't require the decompression valve, though it will make it a bit easier to start. If you have good compression, forget about the valve.
If you open up the headlight assembly, you can see that the ignition cylinder has two connectors to it. One of them holds two white wires (one going to the kill switch) and the other one holds one black wire. I know for a fact that if all of the wires are disconnected the moped will start and run just fine (this happened to me).
Do you get any spark? Check the CDI unit on the right side of the ped under the side cover. It has a small wire that connects to the underside of it to the frame via a screw. That wire grounds the CDI and must be connected for it to work.