Just a note on spark plug caps. I'd noticed that on my R80 machine there must have been some leeking of the insulation- and i was getting severe RF interference on the radio. I actally got a shock off the plug cap too, and the engine was getting difficult to start.
Replaced the cap and eliminated the problems. It's recommended that you do periodically change the caps. I dismantled the old cap to see the effects inside- obviously some spark bridging had eroded away the contacts, and there was a very large build up of carbon.

Also beware that when changing the cap- use one of the rubber ones as illustrated below. The regular ceramic ones are cheaper, but they rely on the screw on top of the plug to stay on. For paramotoring applications the rubber ones are better as the rubber grips onto the body of the plug also for additional holding. You can also improve fitting by fixing the screw top on top of the plug- stopping it from rotating. You can either 'snag' the threads.. or apply a little solder to lock this.

NGK plug caps should be availble from motorcycle/carting shops.