I had the same problem with my 85 Maxim-X, the vacuum activated petcock had screwd up and would drain through the carbs and into the cases if left sitting too long. So, I put in a manual shut-off but in such a way as to have an anti-theft device for just a few bucks. I routed the fuel lines with the shutoff so that it was under the seat in an out of the way place. Easy for me, but not if you didn't know.
When parking the bike at a race or some other social gathering where it was out of sight for long periods of time I'd shut it off, and short of loading the bike in a trailer it would not run for more than a couple of minutes.
For me, it was a cheap, peace of mind solution to wiring a bike for an alarm or $100.00 plus for a specialty disc lock.