I believe the best advice you could get is "have an experienced pilot who knows what they're doing help you". All of this advice you are getting is correct, but the only way you are going to be able to get any real results is to have some "hands-on" help from someone. Although you've been in the hobby for three years, it sounds like nobody ever taught you how to tune an engine. You should never really need to touch your high end needle that much, just one or two clicks each day out should tune it just fine, depending on air temperature changes. You never did state if the air bubbles went away or not. The engine will run when air bubbles are present in the line, but it will never run "correctly". It sounds that you are demanding a high idle. I don't have any RPM numbers, but the engine should idle in the range to where it will ALMOST make the plane roll. The plane should never roll on its own at a good idle. If it does, the idle is too high. As far as needle settings, after you crank the engine and get it to a reasonable idle, run up to about half throttle. Open the needle valve to where the engine will barely keep running, you should do this at full throttle. With the engine at full throttle, the needle valve out enough that the engine is slobbering rich, slowly turn in on the needle until it transitions from slobbering rich to a high pitched whine. DO NOT turn the needle in any farther once you have achieved the high pitched sound, you are now at MAX RPM. Now, turn the needle outward two to four clicks. This will give you a good neutral needle setting. With the engine at full throttle, point the nose straight up. If you hear little to no change, your at a good setting. If the engine RPM drops, your too lean and need to come out on the needle another click or two. Do this untill there is no change in RPM. As far as the air bubbles in the line, if there are any, you've got a hole in a line somewhere. Replace all hoses, even the ones in the tank. The clunk is going to stick in the nose of the tank if the clunk line is too long. With the tank out of the plane, jar the tank forward as if the plane hase nosed in. If the clunk shifts to the front and sticks there, the line is probably too long. And then again, the line may do that every time no matter how long it is, depending on the impact when you hit the ground. In this case, the best solution is to not nose in, PRACTICE on those landings! You have gotten a lot of good advice from all of these guys. I have a 40 LA that was my first engine. It has been nose first into asphalt, nose first into the ground about six inches half a dozen times, and submerged in water and mud a time or two. The engine still runs perfectly even to this day. I've come a very long way since then. It is not a powerhouse by any means, but in "my opinion", they are very tough, reliable engines when tuned correctly. Make sure the engine has good compression, meaning you should have to exert a bit of force on the prop for it to turn over. If it turns over rather easily, you have probably run the engine too lean one too many times and need a new one. If it feels reasonably tight, you're in good shape, just make sure you run it rich enough from here on out. Remember, ther is no substitute for hands on knowledge. You can get a lot of good advice from RCU, but sometimes with so much input from different people, you can be led away from the real problem.

Good luck and don't get frustrated,

John