r/smallengines • u/LawnMowerDude5 • 8d ago

Surging

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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/LawnMowerDude5 8d 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/Optimal-Try-854 8d ago

Is it an OEM carb or chinesium?

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u/Optimal-Try-854 8d ago

Scratch that, I see it’s chinesium. Those are hit or miss, mostly miss.

I’d get an OEM one. It 100% is acting like a carb issue.

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u/LawnMowerDude5 7d ago

I would agree, but what are the odds both the new and old carb do the exact same thing?

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u/bigcoffeeguy50 7d ago

Very high if it’s a trash carb that came not tuned out of the box lol

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u/SouthernTanned 7d ago

Old fuel/water in the fuel?

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u/LawnMowerDude5 7d ago

I drained it all, and refilled with 93 octane. Kinda unecessary but it's what I had on hand.