It's been about 1550km since my last oil change so it's probably due for a change, the oil is at the correct level and I am using the reccommended oil for my bike (10w-40) however. My engine only has inspection covers for the valves, is it safe to run the engine with the covers off? It is starting to look like something other than the valves is causing the noise but it seems odd that this would start right after I adjusted the valves unless if the incorrect adjustment caused it. I don't know how my oiling system works but oil is reaching the valves with no problem as far as I can tell. I tried listening to the engine with a screwdriver pressed against my ear and the noise was louder at the top of the engine and loudest at the intake valve.