At least these aren't too difficult to take apart, here's a picture of the decks after reassembly following those tubes being replaced, the bits that usually dissovle first are visible here as I had to replace them with pink fuel pipe - it was cheaper than the black stuff and fits perfectly:
And the source of suitable tyres, their round profile is fine with silicon sleeves and the o/d won't affect speed as they're idlers so play no part in the gearing, simply being there to maintain direction:
And check the plight of these capstan bushes and their holders, the black goo-fadge is the remains of what came before thae pink sleeves seen in the first picture:
Clean the goo off the bearings with contact spray, a carbon tetrachloride-based one such as that from Halfords which comes in a can with a green label. DO NOT use IPA-based cleaning products around Oillite bushes as that stuff will be absorbed by the bushes and dry them out. Once the bushes and the carriers are clean, soak the bushes in non-EP gear oil overnight to replenish their ability to self lubricate, they will start to squeal if that step is missed.