Engine will run, but it surges, hunts for a constant RPM

1. Partial Blockage of Main Jet. This is for bowl type carburetors only. Stop the fuel flow to the carburetor, either turn off the fuel valve or pinch off the line with a pair of fuel line pinch off pliers or a pair of vice grips. With a pan suitable of containing gasoline, loosen the fuel bowl nut and catch the gas. Now remove the bowl nut and the bowl. Blow out the holes in the nut with compressed air or carburetor cleaner. Some Tecumseh carburetors have a tall bowl nut. Some will have a pin hole in the side of the nut, and some will have a pin hole just above the bottom set of threads. This hole must be clear in order for the engine to run properly.

  • For engines that do not have the jet made in the bowl nut (Kohler, Kawasaki, Honda, some Briggs and Strattons, Onan, Wisconsin-Robin) the jet is attatched to the center post of the carburetor. Some are cast in and others are screwed in. Blow this hole out and blow up the center post to clean the main nozzle. Use compressed air or carburetor cleaner.

  • For all down draft Briggs and Stratton Flo-Jet carburetors (7, 8, 10, 11 HP Horizontal), remove the bowl nut (has adjusting needle in it) and blow compressed air up the nozzle. For Opposed Twin engines, Horizontal and Vertical, remove the bowl drain nut and blow air in that hole.

    2. Leaking Intake Gasket. Check for a loose carburetor or mainfold connection at the block. All Briggs and Stratton engine 3 to 6.5 HP, check the intake manifold for cracking (may have to remove carburetor) or loose connection at the block. You will need to remove the air shroud to get access to the intake manifold.

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  • 4 responses to “Engine Runs, But Surges”

    1. ian younge says:

      Thank you very much, will do what you say tomorrow morning as i tried to mow the grass late this afternoon when it started to hunt immediately on starting the motor. the engine kept running like that and did not clear, so will take the bowl off in the morning. i purchased the engine new in +- 1978 Robin EC10 two stroke here in South Africa our gardens have all been 1/3 to 1/2 acre, replaced with new mower frames, the only work repair i have done to it was a new head gasket. So, I realise i have been very blessed.i also suppose the reason it has worked so well is that I or my family are the only ones to have operated it all these years. in our country it is most common to employ a casual man or lady to do ones gardening. Our son whilst at high school here would mow teachers lawns, we are in Hermannsburg a small German rural village and its school only 17 houses, the school has a piggery and a herd of cows and corn fields and a National Museum of the original german missionaries homestead.

    2. R C Klumpp says:

      i HAVE A 23 HP b&S 725 CC ENGINE ON MY HUSQUVERNA 48″ LAWN TRACTOR tHE ENGINES HUNT AND EVENTUALLY DIES OUT. Ive check the coils and plugs but seems to be a fuel problem Your help would be most helpful

    3. Gerald Tornquist says:

      I just replaced the carb on my 6 hp briggs and straton motor. the carb was new out of the box not a rebuild , the darn thing start hunting. qall ne gaskets new govener spring. I do not know what else to do. any sugestion , will it hurt to run it until I can get it fixed?

    4. Dean says:

      I have a landmaster L140 rotavator needs a new carburetor haven’t got a cluebwhat to order

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