In my experience with modern bikes the branded O type chains available have an excellent life and require little maintenance, and the sprockets are made in incredibly hard steel. Aftermarket sprockets and chains are just as good as oem. 20,000 miles on a 100hp bike used on gravel (dusty) roads ain’t bad. In fact my previous KTM was on it’s original sprockets at 42,000km.
Similar issues exist for modern tyres, vs what we can get for our old brit bikes.
Not wanting to disagree Kiwi about moderns, but here's a sprocket off my XJR - Yam main dealer replacement item at about 250€ for the kit when I bought it some years back. 25K km or 15,000 miles and beyond dead. The original one fitted at the factory did a (little) bit better.
I don't mind replacing things at that sort of interval (although I'd prefer not obviously as it's £$€) BUT it's a lot of work if going the proper route and dropping the s/arm to do it. So anything that would help would be good. (Did someone say 'shaft'?
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I also think it's a poor design in principle to use such small front sprockets with large chain sizes, O ring or other. A hard life is guaranteed for a 16 toother with 100-odd bhp.
I agree about tyres though, as an Avon Road Rider is proving on one of mine compared to TT100s (2.5x the life). Hoping the tasty AM19 Road Runners I just bought for other machines will do better than the Dunlops.
Also hoping that the 5 metres of IWIS 5/8 x 3/8 rear chain I also just bought from The Chain Man following TT's earlier suggestion does better than the short-life Renolds I've been using. Looks the part but the proof of the pudding will be over the winter.
Like you Black Sheep, I find primaries last almost indefinitely if kept oiled. I know people disagree on this, but running dry by mistake now and then has always cost me in busted rollers too. Even with permanently-drippy tin cases, worth the honest stains on the barn floor to keep lubed.