The drop from 7.8hp to 7.2hp occurred upon the first change of the muffler (deletion of the dual port). This muffler still had the .63 inch opening. The Second muffler with cylinder changes came later in 1998 when the muffler was dropped to .43in. with a power drop to 7.0hp. It's seems reasonable that the power loss was the muffler, and maybe not the cylinder. The cylinder may have been modified to stop the power drop being more dramatic....
I'm not seeing any HP change due to ignition coil/flywheel changes. Most of these were first to increase throttle response and ease starting conditions, then later on for emissions. Again, like with the cylinder change, as the mufflers became more restricted, the coil may be working toward keeping performance up rather than down. I have a great chart I can email anyone that wants to see the various Flywheel/coil changes over the years. Email (not PM) me if you want it.
