Before ripping the carb apart,check the fuel line from clunk to engine CAREFULLY,looking for air leaks at all joints.If you use one of those fuel probe filler things,take it out of the system and throw it over the nearest fence,and use a fuel dot.
Make sure the vent line in your system is open.
Next check and clean the screen filter inside the carb.You wont beleive the amount of junk that will build up here and it doesnt take much to throw off a previously strong running engine.
Only when you have exhausted all the above should you have to start digging into the carb internally like the diaphragm.