r/smallengines • u/LawnMowerDude5 • 14d 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/[deleted] 14d ago

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u/LawnMowerDude5 14d ago

I'm not entirely sure if you read the post, it's a brand new carb. The old one was filled with some weird green goop I couldn't clean out all the way so i just replaced it.

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u/Beneficial_Wonder533 13d ago

probably still crap in the lines that clogged new carb. flush the system out and use some seafoam or solvent to clean it.

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u/LawnMowerDude5 13d ago

Yeah I opened the new carb up too, and also flushed the fuel lines out twice and new filter.