I can't recall what the 69-71 steering stop on the frame itself looks like, but on my 72 h1 there's a round section that the lower tree contacts, and it was slightly out of whack (accident?) and allowed the fork ear on one side to contact the tank like you describe. There was no way I was going to be able to pound that straight again, so I picked up a machined collar with an Allen set screw somewhere online (I can't recall for sure, but I may have gotten it from this source http://www.ruland.com/ps_collars_setscrew.asp ) in the correct size so that it snuggly slipped over that frame stop, and this solved the problem.
