UPDATE
So I fitted a voltmeter on the bike, yes I know I really need an ammeter but I just wanted to see if the loads pulled the bike voltage down as they got switched on. I had tested this in the garage measuring voltage and the current draw but I just wanted to see what happened out on the road.
First trip out everything was going well and I noticed the voltage crept up to 15 volts, pulled over voltage dropped and then picked back up to 14.2 with a few rev's back on the road everything fine. Over the next few weeks occasionally the voltage would suddenly rise briefly then settle back down. Back in the garage of course with a proper calibrated test meter fitted nothing untoward happened. The problem started to become worse and more frequent, spikes of 18v occurred, switching the bike off and restarting cured the problem on the road. Obviously voltage regulator fault. Replaced the reg and everything normal.
The reason for the post is, I fitted the meter because I was worried about taking too much power with my accessories despite calculating and measuring actual load when plugged in. The fault was the bike not regulating properly. Whether this was the original fault causing the fire or the fire damaging the regulator I will never know. Fitting a digital voltmeter saved a repeat fire as I would never have known otherwise that that the power was not being regulated and the voltage was rising to 18v
