If your talking about premix, I have always used good ole' Yamalube 2R. I took my YZ 125 in before to get the barrel deglazed after 30 hours of track racing and riding and the mechanics said they didn't even need to do anything.
Peezy, not gangin' up on ya. Agreed, www.Thumpertalk.com is a great bike Forum(s). TON's of bike knowledge there. Once again, make sure to read your manual for the type of oil and the right amount. For me, I like Maxima!
Rotella T synthetic 5w-40. Way less expensive than the bike-specific oils. Don't believe all the hype that you need to run one of the $10/qt motorcycle oils. Had the Rotella analyzed by Blackstone Labs after 10 hours in my 04 YZ 250F and it was still fine. I was going to do the same thing with some Bel Ray and some Spectro, but after about 4 hours on each I could barely shift the bike. Went back to Rotella and all is good. I change it every 6-8 hours depending on my schedule.
What I am doing now is using a Scotts SS filter (Stainless Steel) because it is a good filter and will save me $ in the long run. This is how my oil change routine goes. I am now using Mobil-1 4-stroke racing oil, don't have much test time so I will report on it when I have used it for a bit. But I would change around 10 hrs and if using the paper filter change every other oil change, so at 20 hrs. Every time I would take mine out it was still really clean. Some people change every 3rd oil change btw. Trans I will change every 20 hrs, the clutch oil doesn't get that dirty and the oil doesn't ever get hot or change color (Due to no carbon from the combustion chamber) But still keep an eye on stuff to make sure everything is doing a-ok. And yes clean the strainer and check the magnet! Clean also if necessary.