Brighter headlight for 1980 GS550E ?

[Grimly]

True, but it's only an "improvement" if the voltage was low to begin with.

A quick measurement with a voltmeter at the headlight will determine whether you need to go to the trouble of installing a relay.

By the way, with all the "relay mods" that we tend to do to our bikes, how many realize that just ONE relay will likely do the trick?
Yep, one of the big culprits in the voltage loss problem is the ignition switch. Instead of running all the power for the bike through it, why not just use it to switch a relay that then powers the fusebox, which can retain most of its stock wiring?

Definitely worth considering. My old ignition switch had been corroding at its base connections for a while, unknown and unseen by me. When I rebuilt the front end, the ignition wires were all cracked and corroded severely at the soldered connections on the base of the switch, so much so, given the age of the switch it wasn't worth attempting a repair. I'll replace it with an aftermarket EMGO switch later, but as a temporary measure I wired in a hyster on/off keyswitch. Armed with that, the bike starts better than it has for a while - for the past year there's been a slight hesitation, but now - bursts straight into life first touch. It's also got rid of the slight roughness at some parts of the rev range, which I was suspicious were caused by bad LT connections somewhere, but hadn't zeroed in on them - turned out to be the main switch.

[Miff]

http://www.easternbeaver.com/

I have these kits fitted to a couple of bikes, even with stock wattage 55/60 you will see an improvement. I use a PIAA bulb and high wattage and no worries of melting the ordinal plastic H4 connector, its ceramic.