The main ground cable comes off the stator cover on the drivers side of the engine.
I had both plug wires off the plugs and inserted 2 screw drivers and watched the spark externally. Front one is nice and crisp, rear was wimpy for 4-5 sparks, then nothing. Swapped coil outputs from the dynatek and the problem moved to the front cylinder and the rear was nice and strong, which tells me the coil and plug wire is good. Chased wires and check continuity from the dynatek to the coils and all is good. Next changed the pickup since I saw a post a while back at teryxforums.net with the same problem, still no resolve. I am down to changing the flywheel to see if some weird magnetizing problem makes the pickup sensor think there is one long tooth on the flywheel instead of 2 shorter teeth. I followed the manual on checking the sensor and both of mine seem to read what they are suppose to.
If that still doesn't work I know a guy who knows a guy with a stick of dynomite!