Wilsons Sandbox

Help please. I don't know much about electrical stuff and hope someone can point out a simple solution to my problem. I was doing the routine maintenance on my KLR, including valve clearance along with everything else on the maintenance check list. I've checked the valves twice before and had no problem re-assembling everything and getting the bike back on the road. This time, I replaced shims, then closed everything up. All the other stuff - air cleaner, oil change, balancer tension, fork oil, etc... it all seemed to go fine. So I was looking forward to firing it up and going for a ride. No joy. The motor cranks, but the plug doesn't spark. The plug looks good and was fine before the maintenance work. I tried a similar plug, which also doesn't spark. It seems that the starting system is turning the motor over, but there is no ignition. Is there anything obvious I should look for, something that I might have accidentally disconnected without realizing it? All the connections seem OK. I've never learned to trace wires and current, but maybe I'll have to. Any advice is appreciated. Bryan in AZ