When running can you try giving it a little choke and see if it will rev up? Also, have you examined the hoses for kinks, leaks, etc?
Chances are when you get the filter area all closed up the issue will hopefully go away Sorry for not being more clear, but was referring to the spark plug. Again, may be a long shot, but controlling all things for fire/running properly need to be eliminated...Yeah okay, seems like a good idea, I've been running the carb without the air box and filter even on, just open as it's in a very clean shed so I know no dirt will get sucked into the intake. May have to pull down the carb and inspect further. Also what plug are you talking about?
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