I was riding my bike today on some single track going uphill in second or third gear, when it starting making a really bad clicking sound. I pulled in the clutch and hit the kill switch. We towed the bike back to the truck and I puttered around the parking lot a little bit, ran through all of the gears. The bike started fine and shifted as normal, and had no decrease in power. I got the bike home, pulled the oil filter and it was full of sand from last weekend spent at the sand dunes. (Came in through vent tube) I now have two problems. 1. Where did the clicking noise come form. 2. What to do about the sand. I have since pulled the valve cover off and the the cams aren't scuffed as far as I can tell. Is there anyway to clean the sand out of the motor? Can I just change the oil and run the motor a little bit and then drain the oil and repeat? It also feels like the clutch is really dragging when I pull in the clutch lever. Could the sand in the oil be causing this? This bike has been great up to this point. What do you guys think I should do?