Ok, following a small fire and rear brake failure, I had a chance yesterday to install the new (Galfer) line.
What happened, AFAICT:
There's a plastic "guide" on the swingarm, just behind the rear brake master cylinder. The single screw that holds the guide on became loose, which allowed the guide to rotate (wouldn't do this if there were TWO screws, Suzuki!) into the tailpipe. The guide's job is to keep the brake line AWAY from the tailpipe, apparently, and it seems as tho, owing to the shape and routing of the line, that there MAY be some tension from the line pushing against the guide. IOW, the brake line may always be putting pressure against the guide, such that if the screw loosens, the line pushes on the guide, causing it to pivot into the pipe.
IAC, once the plastic guide touches the pipe, it melts/ burns and allows the brake line itself to rest against the pipe. The brake line cooks thru, and you lose all pressure in the system. Pushing the pedal pumps fluid out of the burned thru area of the line and squirts it directly in the area where it has burned thru - which is, by definition, the area where it's touching the hot pipe.
Some combination of hot pipe + plastic + brake fluid enables open flames - which is pretty disconcerting, even if it's in a really localized area and you can literally blow the flames out (which I did).
Correction: move the guide back into position and tighten the screw.
Better corrections (I haven't implemented any of these): add a second screw somewhere on the guide to prevent it rotating even if a screw loosesn; fab a larger guide - perhaps of metal; re-route the brake lines somehow; and (what worked for the limp home) zip-tie the brake line on the inside of the subframe so it can't flap around near the pipe no matter what happens.
The guide swung over into the pipe - you can see where it's been melted/ burned away.
The guide in it's proper position:
The cooked line:
Now, just to prove that he hates me, God arranged a few other challenges - after putting everything back together, I was re-installing the seat, which involved a slight push forward, which was enough to push the bike off the sidestand and cause a dump in my driveway
I also lost the clutch lever in this drop.
Very much daunted, I pushed the bike back into the garage as I was running late for work. Pushed the button for the garage door opener to close the door and heard a giant crash.
One of my garage door springs broke and smashed out a window in my garage door.
Our house is on the market, we had a showing in an hour and half, and I was already running late for work.
I don't know what I did, but I'm working some kharma off, evidently.