Also, on a side note the powervalves look perfect every time I go to clean themQUOTE]
Yamaha's exhaust valves are self-cleaning. Every so often they do a scraping cycle, not sure how often that happens but Ive heard it happens every time you start the engine.
Ive heard a lot of good things about the longevity of YPVS (Yamaha Power Valve System) and to me it seems to be a lot better than some other designs.
Ski-Doo's R.A.V.E was pretty pathetic and was known for having one valve open more than the other. Polaris' VES (variable exhuast system) seems to be pretty good. Almost all the sleds in my family have VES and its great. Cant complain about more power with better milage. The only thing I dont like about VES is the frequent cleaning that is required. My brother ran his '97 440 XCR for 700 miles and the valves were so gummed up that he had a hard time getting them apart. Ive heard that Polaris now uses titanium slides that dont stick as bad. I still wonder about wear though. Titanium slides in an aluminum block...
Hebi