Roy Halliwell asked me if I could soften the carb inlet rubbers for his CB350F in the Reofos 50 stuff I use. Problem is that they also have rubber to metal bonding that could be degraded by the chemical used. So rather than totally immersing them I put them in a tray, metal side up and then filled up to 3/4 the height of the parts. What I find is UK bike rubber parts soften quite easily but USA bikes from hot areas are much more difficult to treat. Anyway they have now responded well and I also post treated them in free air in an oven at 100 °C for 4 hours. I then tried one on a scrap 400/4 carb body with a new clamp and it gripped really well. I will get them in the post Roy so you can get that lovely little 350/4 up and running again.
BTW everyone Roy is resorting to this because Honda ones are very expensive and the Cruzinimage ones he bought have disintegrated after only a short period of use ... you have been warned !