It has to be a labor of love, because when you look at the economics of restoring an old bike the numbers don't work.
A few years ago I picked up a great deal on a complete 1987 K75Cs with 23k miles--just $400. The "only" problem was it was left for dead sitting outside unloved and uncovered for over a decade.
Last April I finally got serious about bringing my "Zombie" bike back to life and just finished most the the restoration about a month ago. The total costs ifor the bike and parts--$3177.66. At best the bike is worth $2750, probably less.
The restoration was thorough and since I plan to keep the bike a long time I went the extra mile "renewing" serviceable parts like coolant hoses and rubber boots and rebuilding brake calibers that I didn't have to. At the same time I looked to economize by buying used and aftermarket parts where I could. And there were a few expensive maintenance items included such as a battery and tires, and I added some accessories such as a top and side cases and the 50 amp alternator which all pushed the costs up.
But was it work it?
The bike is wonderful and I plan to keep it a long time--it's smooth as glass and with the stock pipes quiet too. I commute by bike to work and have parked my '99 K1200RS and adopted the K75 as my daily driver.
It must be love, because in the end, I'd do it again even though when I add it all up, it just doesn't add up!