re: removal of the old gasket material, I like using a hard plastic drywall taping knife or putty knife... not metallic!
I'll liberally wet the gasket with WD-40 or PB-Blaster and gently scrape it off. then use the Scotch brite pads... after all the 'gunk' is off I'll use isopropyl alcohol to clean off all the WD-40 residue.
usually due to the heat/cool cycling and age if you can get an edge of the gasket lifted you can slip/slide the edge of the 'knife' up & under the lifted edge.
OR, if you're handy with a new razor blade scraper that works well, but they're less forgiving in case of slips... (don't ask).
sorta bulldogged custom 1978 GL1000 - "geekster" - daily rider
full Vetter dress 1979 GL1000 - "Barge" - daily rider (currently down)
1986 1200 Aspencade - "Heart of Gold"
1990 1500 Aspencade - It's ALIVE! but with a green drool...
1978 for $100 - project in worx
1978 from a previous member here - taking up space
my original '79 bought in '91 - replacing engine (eventually, maybe someday)
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The good thing about science is that it's true whether or not you believe in it. ~ Neil deGrasse Tyson