I'm changing my rear sprocket and chain today and noticed that the rear sprocket is not hardened. At work i have all the sprockets i use hardened and I get 3 times the life out of them. Is there any reason why you could not have the rear sprocket hardened?
I put 98k miles on a CM400A, 80k miles on a CB750K, and 80k miles on a GS500E without ever replacing a rear sprocket, never had one worn enough to require replacing. I do replace the front sprocket every or every other chain replacement though, they are worn and need replaced. Think a new OE sprocket should be good enough as is unless you never lube them.
Chains and sprockets are sacrificial components in that they will eventually wear out. I cant see a problem with hardening sprockets as it wont affect the way they function, so long as they are not so hard they become brittle. A hardened sprocket will cost more and may well wear the chain out in less time than a normal `soft` one will. Any savings made in the form of an increase in sprocket life may well be offset by the reduction in the chains lifespan and remember chains cost more than sprockets. I think if there was any serious gains or advantages the sprocket makers would have cottoned on to it by now and be shouting about the fact.
You should always change the chain and sprockets as a set. A worn chain will wear out new sprockets faster, and worn sprockets will eat a new chain. As for runsilent's experience, that is damn good. I have never, ever gotten any kind of mileage even approaching that out of any bikes that I have ever had, and I have had over 30 of them. Most of the time, I run the sprockets until they are so hooked that the chain will hardly roll on them.
There is a company that makes sprockets out of tool steel that are supposed to last forever. Ironman, I believe. But I think they are only for dirtbikes. On my streetbikes, I always run a steel rear, usually Sprocket Specialties, or someone like that, and a good front, stock or Sprocket Specialties, and since the late 80's, always a DID chain. I've had bad experiences with both RK and Tsubaki, and really shitty customer service by both companies.
Getting a hardened sprocket is not a problem if you know how to go about it. There are plenty of Gearcutting firms out there in industry who will manufacture a 1 off sprocket to sample out of any steel or even Engineering-plastic you want, and there are also plenty of Heat-treatment firms who, if possible will harden it to any degree of Rockwell, Vickers or Brinell you want......assuming of course you are prepared to pay. But the question remains.......what are the advantages of having a hardened sprocket? It will only pay if you get say x2 life out of it, for less than x2 the cost of a standard one, and that assumes. A) You intend to keep and use the bike for the life of 2 sprockets. B) Any potential reduction in the chains lifespan is not included. C) The labour cost to replace the sprocket (assuming you dont DIY) is also not included. The sums dont add up for me. I will stick with the standard ones.
Sledge, absolutely right. I don't know about the UK, but here, custom, one-off machine work and heat treating are not cheap. In fact, it is not even reasonable. When you can buy a good steel sprocket for $35 or so, and shop labor here is about $75/hour, it gets prohibitive, to say the least.
And really now, how fast does a sprocket on a 38 HP bike wear out? Mine has 22,000 miles on it, probably has about 5 thou left. That isn't too bad.