Mini places like Karcraft sell new rack boots as a pair, they are pretty cheap.
Undo the tie rod end, and the boot clips. remove boot, fit new one and tighten only the big clip.
Then stick a pump action oilcan nozzle inside boot next to the tierod, and pump some oilz in there.
I use 90/140EP or whatever heavy gear oil I can get.
Move rack from lock to lock, if you have put too much oil in it will squirt the excess out. Then refit the small clamp.
I have done this on my 1970 original rack a few times over the years, it has now done ~140,000 miles and is still not loose.
Modern rack grease can be used in Mini racks, but best to do that on assembly. If it's an old oil filled rack I'd just top up with oil.
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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.
