Carbureted B&S 31 HP Vanguard engine model #543477-3048. Purchased new in 2016 has 400 hours of use. Well maintained, regular oil changes.
Symptoms are misfire & irregular firing, will not idle down, will over-rev (past 3300 RPM), occasional backfire upon startup.
Generally happens earlier in the morning when it is cooler out and then as day warms up the engine will run like a top. Perhaps the weather issue is also barometric pressure related. Never really notice any performance issues during the summer, only spring & late fall.
Have ruled out the basics (i.e.: new spark plugs gapped to spec, new air filters, clean rec fuel)
Co-worker thinks the engine is running rich and needs carb adjusted or worked. I noticed this engine has two air filters ... I've thought about removing one of them and see if it runs better but have not tried this.
Please offer advice on where to start troubleshooting.
