Jack, I think it's more ass covering so no one can sue and say, 'well it wasn't in the manual that said it has to be changed.' So they pile on the shelf life more or less so if someone goes down on a wet-cracked hose line, show the receipt it was ever changed, now 20 years later you begin the suit?
Because you know that 100k bike with all those miles, that means he's gone thru so many radi hoses 'buy' now, and oh, lookey there, the same original hoses that came with the bike... just saying. They don't say to change the drain lines off the gas tank and that's pretty much the same kind of rubber quality. How come no change in 3k for those?
So with all the bike brands, the non-replacements or the lack of following the manual replacing radi hoses for decades now, this is just as an example. Lets change rubber to the brake hoses and there are still the same old brake hoses running around on old Z-1 bikes say. It has to pass DOT, so that's quality oil resistant rubber, as opposed to the black deterioration of the brake diaphragm rubber turning the oil black on some 14's.
That's what you want to look for. Rubber has memory for so long, springs back, etc. But then it gets old, stays compressed, begins to crack. With water/oil turning black, this might be where manufacturing rubber and EPA begins messing around with the formula and now Japan is in on it too? The good old stuff that lasted longer is gone. Now it's a continued plan obsolescence shortened even more?
Tormenting the motorcycling community one post at a time