A traditional problem of restoration has been the deterioration of rubber intake moldings. There is a way to reclaim neoprene rubber components that have hardened with age. The problem is that the synthetic rubber contains plasticiser chemicals, which keep it supple, and these tend to bleed out over the years.
The answer is to soak the rubber in a chemical that will replace the original plasticisers and restore it to its original pliable state. The chemical is available at any camping shop….the silicone waterproofing that is sold for re-proofing tents.
The technique is simple: Soak the rubber all over with the silicone spray, pop it into an air tight bag and let it soak for a few days. You will find that the proofer slowly soaks into the rubber and restores its original suppleness. On badly hardened rubber you may need to repeat the treatment.
Soak part for 24-36 hours in a mixture of 30% wintergreen
oil (methyl salicylate) and 70% xylene.