I think the 10 hour service is where the valves should be checked. Checking is easy, you can do that yourself, your dealer should certainly do it. Then, if something is out of spec, they can catch it then, before any damage occurs or performance suffers or both. I suspect few actually need adjusting at that point, but they should be checked. Unfortunately, unless you have shims etc. any readjustments should be left to the dealer.
The one big disadvantage of the DOHC set up is the difficulty in adjusting the valves. Ah well, the price we pay for a fabulous motor.[img]i/expressions/face-icon-small-smile.gif[/img]

 

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2) what is the procedure for changing the oil, and how often should I change it. How often Do I change the filter?

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If you're the type who likes to keep your bike show room clean, you're going to hate changing the oil. You might as well just baptise the entire quad in old oil before you start (slight exageration). After the first couple of times you realize there's no neat way to go about it. If you think the DS is bad, try cleaning the air filter on an XR50 (UGH!!). I change the oil filter every time I change the oil, every 8-10 hrs.