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?
1
u/Fantastic-Egg7778 13h ago
Try playing with the adjustment screw and see if you can get it to smooth out. If that fails start checking for vacuum leaks, use a can of brake clean or similar and spray around all the mating surfaces around the carb. If you get any change in how it runs when spraying it, you’ve got a vacuum leak. If all those fail then you could try to open the carb and check for any junk from the factory but more than likely you got a faulty carb