2) To kick one's ass, typically as revence for a former deed.
3) to repair something that is broken
2) So Johnny broke your windows, eh? we’ll fix him good then.
3)if it ain't broke, don't fix it
The Fix could be brought out right in those days at some bike stores by asking for a racing bike. Racing bikes were usually made by Bianchi or Lotus and sported rear facing dropouts for the back wheel; these store bought Fix bikes were uncommon for the average fix rider and primarily purchased by bike messengers.
The majority of serous road bike riders, then and now, use geared bikes.
Today people are calling bikes like this "Fixies"; there was no such term ( fixie ) being used on the streets in 1970's thru early 90's.
Fixie should be used to describe store bought bicycles many of which do not even have fixed flywheels.
Joe has a Fix with no brakes.