A week or so ago I removed the forks to replace the seals, and found this. The plastic fork stone guard has been quietly wearing away the aluminium slider. After replacing the seals and setting them up as per kiwiape's post I re-installed the forks followed by the left guard. Then I heated the guard at the flap edge and bent it out in the hope that it would clear the slider. When I attached the brake line to the guard I discovered the culprit. If I simply screwed it into position it put a rotating torque on the guard. To remedy this I put a counter-torque on the cable before tightening it up. This stopped the deformation. I think I was successful, but time will tell. Anyone with a Terra should check this out.
I haven't tried it out as the bike is unregistered at present. I don't plan to put it back on the road until after Christmas when I've got a couple of high country rides planned.