My experience with chains (non-oring) on dirt bikes was good. I decided to stick with the non-o-ring types for my Ducati when I bought it. I kept the chain clean and well lubricated but both the DID and RK chains that I tried didn't last more than 5,000 km.

I then decided to switch to a Regina x-ring chain for the Ducati and I think that's got over 14,000 km on it now and I'm not having to adjust it all the time, either.

I recommend Lanotec for lubricating chains, though I think it's only available in Australia.