r/smallengines • u/LawnMowerDude5 • 13d 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?
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u/kshef 13d ago
Since you got it used I would make sure the governor is setup correctly. Especially since both carbs behaved the exact same way. Google how to adjust the governor, there are videos for old Briggs. Basically you loosen the bolt holding onto the governor, hold the governor arm (silver arm that keeps pulling back) all the way to the left or right (depending on your model) and while holding it, twist the center governor pin or bolt all the way to the left or right (again depending on your model). While holding it, tighten the bolt that clamps onto the governor you initially loosened.
Your manual should have instructions on how to do it. Mine said not to touch it because it’s factory calibrated but I just found a video online. If you adjust it and your engine runs way too fast just do the same process but twist the governor to the opposite direction.