i forget did you take the head off?? sometimes you get "coking" on valves that have oil leaks,and improper carb settings. it might be that the coking is starting to interfear with valve action... with the BG44k see if you can get a decarbonizer that is sucked up through the intake and there for through the intake tract and valve. i know that jiffy lube can do that for you, i just made my own metering setup with a main jet and some vacume hose.. it worked pretty good too.