How I fixed mine:
Fairly easy fix. My '87 512 had 3 cracks in the rear cable routing opening. The tube was almost broken in half.
Anyway, what I did was find a donor frame, and cut a 6" section of steel tubing out. Then cut the section of tubing lengthwise into two halves. Drilled a hole for the cable routing. Placed two sections over the crack in the frame.
Bought a $50 MAPP gas torch, silver brazing rod and flux. Brazed the two halves over the cracked section of tubing. Touched up with rattlecan. Frame fixed for under $100.
