Bought an 08' XR650L used with 600 miles. I rode it home, did an oil change with Honda GN4 10-40 and a factory filter. I rode the bike for another 600 miles, this took several months over the winter. I found the service manual online and read that the bike could also run 20-50 which is what all my other bikes run. I switched to Castrol, installed new factory filter, and started her up to warm up. It made that odd clicking sound from the oil pump area. Other posts suggest that it is the oil pressure bypass, many Hondas do this and that it goes away after 30 seconds or so, once the oil starts to get a little temp built up. I rode the bike around the neighborhood and came back to check the level. I added a little to get the right reading on the dipstick and started her back up. It continued clicking for the same 30 seconds or so, again I ride around the block. The next morning I decided to ride her to work, but upon startup the clicking never really went away. I shut her down after about 2 mins of running, hopped on another bike and came to work. When I got home, I decided to drain the fresh oil, and just go back to the 10-40 since my problems seemed to have been associated with the oil change. I decided to pull the filter and drain that area and was suprised to find the factory filter compressed about 25% and all the pleats wrinkled. I came over to my trash can with the filter and noticed that the oil would not run through the element. I took another new filter, poured some 10-40 in it and out it came. The older manual online says 20-50 for appx 32 degrees and up. It was 60 degrees during the problems I ran into. So tonight, back to Honda for some 10-40. Sorry for the long post, just sharing my info. Everyone else runs 20-50, thought I could too.