I beg to differ. Most newer jap cars run 5w 20 or 0w-20. They are also very soon stocking 0w-10 oil.
I run 0w-40 Full Synthetic in mine, and I don't care what you say, I have all the papers that PROVE that the oil I use runs cooler and IS compatible with wet clutches AND won't break down like conventional motor oil.
You're living in the dinosaur ages my friend. There are plenty of synthetic oil ATV users out there who will disagree with you. The old synthetics are NOTHING like new synthetics. You seem to know a lot about 4 stroke engines, but the way you try to push your opinion, based on SOME truths is quite misleading.