I had the same issue when dismantling the tank on my 620. So I made this out of a piece of MDF. I used the fuel cap as a template to drill the holes, then just screwed in the long bolts. it gave plenty of leverage with a hand hold on each side to 'wiggle'. It came off quite easily. I used the same method to reposition it. Don't forget the red rubber grease. Having this made it easier to perfectly position it parallel, couldn't stand to look down and see it slightly wonky. Hope this helps if you've not got it off already?
