My question is about this 'H' adjustment, which I believe controls fuel flow at high speed. I can get it to rev properly by unscrewing the 'L' screw further, but then it won't tick over so that's clearly wrong. The 'H' screw makes no difference at all whether fully open or fully closed.
If I get it running nicely at tick over, it won't rev up properly. I've fitted a new plug as a precaution, and cleaned the air filter before trying to adjust the carb. Recently it's been giving trouble, getting hard to start and not running well. The handbook gives quite clear direction on carburettor adjustments which are the normal idle speed, 'L' and 'H' screws as found on similar small engines. We have a McCulloch MT320 strimmer, not sure of the age but probably over 10 years old.
