I have never wired a really old Harley...but from the mid 80's up to the pre "fly by wire " models... the only reason the handlebars were grounded is because the stock turnsignals were mounted on the bars...none of the switches/controls require a ground. If your turn signals have been moved off the bars...really doesn't matter if they are grounded or not. The front end needs to be grounded, so the current is not going thru the bearings, but that is usually addressed thru the headlight wiring. I am wiring a Volkswagen trike as we speak.

 

On my bagger I was having charging issues... Needless to say I replaced all the charging components. But I was having initially problems with my turn signals not working intermittently. Chased it out, turned out to be lights ground through the chrome on the indicator housings in 91. Wired a ground to the frame inconspicuously. Works great.
I was having a 2 volt drop from the battery to everywhere.. traced it back to the ignition switch. All it was was grease from inside the switch melted down (probably got hot with the bad grounds from the turns b/c everything else checked out). Cleaned it off, got only .03 volt drop through the ignition switch.. within limits of .01 to .03. Harley made a ton of money off bad ignition switches from what I researched on here. If its not that its the turn module. Well, I dont have the funds to put out 120 for a new box. So I took some terminal ends, and a couple cheap flashers wired them in. I don't have hazard lights n have to hold switch in to execute the signal. Fine with me because I rarely use them except at night. So used to hand signaling.
I sat and figured out what it would have cost if I took it to harley... Ignition switch 150 (they would have to call other dealers to see if they have it b/c its obsolete).
120 for the turn module
400 for the rotor stator and reg. (which I bought)
and probably about 4 to 6 hours @ 95 bucks an hour to do the work.

I did it all for just under 500 bucks. When I come across another stock module, all I have to do is unplug the homemade harness, and plug the box back in..
Just have to be 10 percent smarter than what your working on!

I recommend checking all the grounds for resistance causing stuff whenever putting the bike up for the season. Look at the battery terminals, all ground points, fuses, terminals for corrosion, dirt, oil or anything that looks like it will cause resistance. Cheap insurance and unclicking the terminals once a year for inspection keeps them free so when you have to unhook it, its not a pain in the a$$. Especially with these old bikes without the deutsch connectors.