This morning I was able to talk with my mechanic regarding changing the spark plugs on a Stallion Trike. His instructions were to unbolt the cruise control servo and move it to the side. Then remove the ignition coil completely. In order to reach the back one you will need a long universal spark plug socket. You can get the other three with a three inch extension.
He found on mine that there is a cylinder head temperature sensor that is located between cylinders two and three, and there is a rubber seal that goes around the wiring harness that goes to the temp. sensor and my plug was not in place and it was letting water gather in the valley where the spark plugs are located.
This water was allowed to sit there and rust the plugs to the cylinder head. He either replaced the rubber plug or just put the one that was there back in place and I should not have any water issues around the plugs from now on. The engine runs as smooth as silk after the plug replacement.
I hope this is helpful to those of you who asked for the above information.