Just some info on my stupid experience. I replaced my 216's head last summer and have been on and off trying get it to run smoothly. I adjusted the valves several times, worked with the timing, even replaced the carb. Today I went to get non-ethanol gas for winter storage. I still had an intermittant "pop" in the exhaust. Figured I'd double check the valve adjustment again. This time I noticed that the front bolt holding the rocker assembly was loose. I could actually wiggle the rocker shaft. Tightened the bolt, readjusted #1 and #2 valves and now it is running better than it has in literally years. I don't know how I never noticed that loose bolt, I know I torqued it when I swapped the head last summer - but I never re-checked it. Just goes to show - aargh. Easy simple thing I never checked - double arrgh!
