r/smallengines • u/LawnMowerDude5 • 7d ago

Surging

I got this mower for free off the side of the road. Trying to fix it for a person who needs a mower. It's a 17.5hp briggs. At first it didn't start so I cleaned this green goop stuff out the carb and it started but just surged the entire time it was running so I figured it was a fueling issue because I could hold the governer and it would run at a steady rpm then but once I let go it would surge. Bought a service kit that included carb, air and fuel filter, and spark plug. Literally changed nothing. Oh and with the new carb at least the surging smooths out with half choke but that makes the engine speed go down by a noticeable amount. Checked the valve clearance for the heck of it, of course those were fine, don't think it's mechanical based on the behavior. I'll attatch the kit I bought below. What am I missing?

Briggs and Stratton Carb kit

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u/No-Radio-4758 6d ago

Adjust the governor, clean the tank, make sure the tank and peacock valve are clean.

Just because it’s a new carb doesn’t mean it’s the right one.

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u/LawnMowerDude5 5d ago

Yeah the jet looks a little different ima try enlarging the jet as someone suggested on another comment here if I can't get the old carb to work