If the selectors have suffered a "ductile" failure, where the material has migrated from the top fork to the bottom, do not replace the forks without replacing the sliding gear as the new selector will pick up on "invisibly deposited" in its slot and cause a similar failure. I once managed to scrounge a second hand set of used selector forks to replace mine which had failed on the way to a Kenmore rally. The kind donor who was a friend of a friend of a total stranger had a Square Four and a Panther and I think they both had BAPs. The friend (of both the donor and the total stranger) whose petrol station I had stopped in to strip the gearbox, drove me 70 miles to collect it. The donor drove me 70 miles back to find that the service station was closed and my Comet had gone. Somehow I tracked down the address of the Service station owner and was taken there, where his wife cooked a meal for both me and the donor/driver. I then rebuilt the gearbox. When I had it complete it didn't want to change. I asked the owner the time and when he told me it was 11;30 I said something along the lines of " Oh well, its too late to even buy you a drink". He didn't accept this and took me into town where the only light was Blue outside the police station. On the other side of the road was a hotel. He hammered on the door until they opened up then we were led, in the dark, through to a lit and populated bar where "afters" were had.
When I rode on the following morning the gearbox quickly became a two speed, third and fourth I think.
I arrived at the rally as everyone else was going home on the Sunday and then rode with Rab to Glasgow where I eventually got an RAC recovery sorted. I missed work on the Monday as I didn't get home 'til mid morning. When I called in to apologise for my absence the works manager said "Never mind, did you have a good time?"
I could only reply "Incredible - unbelievable"