Topic: '78 CB550K - Stupid question, probably

[CrisPDuk]

OK it's dumb-assed noob question time

My bike is a bos stock 1978 CB550K, was this model fitted with a cushion drive assembly in the rear hub?

I can't check for myself, because I'm working away from my bike at the moment

[edbikerii]

Yes

[CrisPDuk]

Thanks

My next question, based on that answer is;

Considering they are probably the original items, and the bike's done nearly 50k miles, should I replace the rubbers?

[CrisPDuk]

Anyone

[Gordon]

Is the rubber still pliable or is it hard as a rock?  When it comes to something like the cush drive, seems to me like it's more of a personal preference than a required replacement. 

[CrisPDuk]

I don't know to be honest, the rear wheel hasn't been out while I've owned the bike.

I'm in two minds at the moment. On the one hand the wheel definitely has to come out, because the chain and sprockets are desperately in need of replacing, but on the other, there's no need to take the hub apart because the brake works and the bearings are fine.

So do I do it now, or do I apply the 'what aint broke' principle and leave it until next winter, when the whole bike is coming apart to undergo a total rebuild anyway

[Short Round]

leave it for the total rebuild process unless you suspect there is a major problem.  If there is no problem, do it this winter when you are restoring, that way you are in the mind set of doing things the right way (and the long way).

[nickjtc]

If you are smooth on your up- and especially down-shifts (as in, matching engine speed to driveline speed) then the rubbers are never being called into play; so it's a job which could wait until next winter.

[billstron]

What exactly is the cushion drive?  I have the same bike, and I had the rear hub apart when I first got the bike.  I didn't notice any rubber in there, but then again I wasn't looking for it. 

[Gordon]

What exactly is the cushion drive?  I have the same bike, and I had the rear hub apart when I first got the bike.  I didn't notice any rubber in there, but then again I wasn't looking for it. 

It sits directly behind the hub on the sprocket side of the wheel.  If you pull on the sprocket when the wheel is off the bike, the hub will come off and you'll see it.  It consists of several thick pieces of rubber that form a cushion between the part of the hub that's attached to the sprocket and the part that's attached to the rest of the wheel via the spokes.  It's basically meant to soften jerky accelleration and decelleration.