When we talked about this bike before, I did some reading of Euro tests and IIRC the valve interval was 8,000 mi. That would lead me to think it was screw ajusters. Which isnt a bad thing if the valve cover comes off fairly easily, depending on radiator mounting, etc. Chains, unfortunately, are cheep to make and lightweight. But are a complete maintenance headache, o ring or not. When I looked at the Suzuki SV650, he dealer said he reccommends they (chain and sprokets) get replaced at 10,000 miles. Sounds like a good way to make money if you are a dealer. This may not be possible anymore, but my Yamaha XV920RH Sport touring bike had a fully enclosed chain running in a lithium grease bath. I hardly ever had to touch it and I never replaced it.