Thanks for this - My YLM 342 stopped after 20 years, hadn't been serviced for 5 or 10 as the local supplier shut. Thanks to your pics and some other general help I removed the carburettor dashpot and found lots of crap in there, cleaned out, changed oil but now it's running like a hare, even on the slow tickover. Would that be the governor not kicking in? I don't want to change the screws as it was fine till I stripped it down.
I took the airbox off and it ran slowly again, I can't tell if the airbox is sticking on the governor linkage or just having cleared the carb and mounted tightly it's now over fuelling (I did put the plate and nuts back on to keep all the carb gaskets sealed). One other thought - is it possible I've bent the float?
Thanks in advance - it's the first time I've stripped one down and TBH I amazed my self it's running at all!