I made a post about this a couple months ago but I'm still having the problem, so I thought I'd bring it up again. My valves chirp sometimes, like a cricket. I've heard many opinions on what it could be, but my local shop repair man checked through all the ideas, and couldn't find anything. I was just given another idea recently about air filling in the space between the valves and the valve casing and said I should use heavier oil. I don't really have a clue as to how it all works, so I thought I'd post the question here. If that could be it, what oil should I try? Right now I use Blue Juice.