Hi,
Here's something else to try - locate the starter solenoid - its bolted to the rear fender and lives deep under the seat.
Peel back the rubber boot that covers the electrical connections on the top of the solenoid and ....... making sure the ignition is on and the bikes in neutral first (!) bridge the two large terminals with a screwdriver, one equiped with a wooden or plastic handle mind.
Only do this momentarily otherwise you will weld the screwdriver to the terminals
.
If the engine turns over when you bridge the terminals then you have an issue with the starter solenoid not the decomp solenoid and valves. If you are lucky its just a discharged battery, if not then the Clymer manual tells you how to test the integrity of the starter solenoid and its easy and cheap enough to replace.
Also, by the sound of it the bike suffered some trauma around the starter motor area so it could well be worth unbolting the starter motor and making sure it will turn freely, it could be stuck.
And one other thing I have just thought of - does your bike have to start with the clutch in? If so make sure the connections on the handlebar switch are sound and remember that if the bike is in gear and the side stand is down, the bike won't turn even with the clutch safety switch activated (there's another one on the side stand to prevent you riding off with it down).
I hope some of that helps chap.
All the Best