Cut away on the whole pile, brother, unless the tools are worth more, or you like parting things out.
*The Yamaha is a V4 cruiser, 1300. If it's got bottom end problems, you're looking at a crank and 4 conrods. Fucking nightmare.
*The ZG1000 Concours wasn't really a good bike. There's still a few out there, but people aren't really looking for parts to restore those things. Drive it 'til it dies, dump it for another bike. You won't get much from parts.
*1985 Vulcan 700 - you can't even find parts for it. Kawi discontinued most of the parts supply for that bike several years ago.
*KZ550-F2 Limited - another turd from Kawi in the mid 80s. Cut away. Even with a new engine, you'd have more into labor in putting the new engine in, than the thing is worth.
*1996 KZ1000 Police bike - these things have been trashed through the years. I work on them often - mostly from people that are into the Patriot Guard riders - they need to get these bikle back up to full-police certification in order to be an escort for the organization. I've seen dudes dump TONS of money into these things, just because they got them cheap, and they support a cause. Supporting the cause is noble as fuk, and I admire the hell out of that, but they should dump more money on more bike, instead of looking to get into it with a cheap bike - that costs them a ton.
Anyway, my $0.02. <thumbsup>
EDIT - i no-$hit had a KZ1000 Police bike in the shop last month... nightmare with wiring, with all the cop-wiring in it. I just had to make the damn turn signals work, and it cost the guy a small middle-eastern fortune.