FPD218, thanks for the msds, I'm not a chemist but that looks like standard ethelyne glycol, correct?
Latebird, thanks for sharing your experience. I'm shocked that that 97 XR got so hot. I was under the impression that the dry sump arrangement helped to control the temperature better, but apparently not. I use synthetic for the cold start flow and longer drain intervals on my cars, but that highlights another reason to use synthetic in small engines. Currently I just use mineral oil in my ATVs and change it very often. but am thinking about switching to synthetic. I use rotella by the way..
About valves, your experience matches mine. I haven't owned a unicam CRF, my brother does and he loves it, but he is always in that engine (sometimes because it needs it sometimes because he's after more power) most my experience comes from working in an independent powersports shop from 07-13. We had alot of unicams through that needed valves a few that ruined the seats. If the head was good, then stainless valves seemed to give the best longevity. Granted alot of those bikes were absolutely thrashed. I can't think of one Yamaha that wore the valves out (maybe I'm just forgetting because its convenient lol) the 5 valve yamaha heads are all coated Ti valves as well intake and exhast. they still fail of course but were catastrophic failures related to people thinking that the rev limiter should be tested frequently, and not changing pistons.
I agree, you have to choose the right bike for the intended purpose. But I have a problem where I want the best of both worlds, I want the power, light weight and suspension of a motocrosser, but a wide ratio gearbox, decent charging output, and a radiator fan big enough to keep up.. I'm currently without a dirt bike, as ATVs fit my requirements better ( where I currently live there aren't many single track trails) I'm currently weighing my options but most bikes that fit my requirements don't fit my budget for a dirt bike, suprise suprise lol. I like the BRC 500 the best right now, the new yz450fx, wr450f, and ktm 300 xc-w are on my list of contenders. I also detest the tire maintenance of dirt bikes and like riding in sand and snow, so I'm very interested in the big wheel conversions and snow bike kits. It will probably be a while before I get another 2 wheeler though. I'm enjoying switching between the yfz450s and the big bore 4x4 ATVs.