My mower is still surging after replacing the plug and fuel line/filter. At times it runs real smooth and feels strong. Usually under a load like climbing hills and deep grass will cause it to start surging and then it wont go away. When I get off and look at motor the spring seems to be going back and forth. Is there a way to adjust the carb to fix this?
12 HP Briggs IC surging
- Thread starter spk2000
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Seafoam
Your carb is dirty or clogged
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- Nov 29, 2009
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It's not getting enough fuel under load. IE clogged carb. Pull the bowl off blow out the main jet, then put it back on.
You probably have carburetor problems. Take it apart and clean the internals, see if it helps.
Before taking the tools out go to Walmart or parts store and grab a can of Berrymans Chemtool, put a good splash in the tank and let it run, it will probably clear within 15 min. Don't bother with Seafoam it does little more than make smoke.
https://www.walmart.com/ip/B-12-Chemtool...13=&veh=sem
https://www.walmart.com/ip/B-12-Chemtool...13=&veh=sem
I have a 20 yr old briggs engine, on a rider mower,,,this happens to me a few times each summer,,,I remove the adjustment screw on carb, spray and clean our\t hole, and clean screw and put back in carb....its mainly fine dust and junk, runs fine after that, ,
Check the vent on the tank cap as well.
Originally Posted By: mk378
Pull the throttle lever on the carb fully closed against the screw stop. It should run slow and steady. If it dies, the idle circuit in the carb is clogged. That will cause surging.
Yep.
The first thing that you should do is make sure you are using FRESH fuel (not fresh from your gas can, fresh from the gas station), but, you likely have a restricted/plugged low speed (idle) circuit in the carb. The spring going back and forth on the carb that you are describing is the governor spring, it is going back and forth because the governor is responding to the fuel/nofuel situation going from the main jet to the idle circuit. mk378 is offering valid diagnostic advice. Putting something in the gas will NOT solve the problem, the restriction needs to be physically removed. Another thing that will cause this is a worn-out throttle shaft, which is a common problem on this engine when it gets old. Check the throttle shaft for excessive looseness in the carb body.
Pull the throttle lever on the carb fully closed against the screw stop. It should run slow and steady. If it dies, the idle circuit in the carb is clogged. That will cause surging.
Yep.
The first thing that you should do is make sure you are using FRESH fuel (not fresh from your gas can, fresh from the gas station), but, you likely have a restricted/plugged low speed (idle) circuit in the carb. The spring going back and forth on the carb that you are describing is the governor spring, it is going back and forth because the governor is responding to the fuel/nofuel situation going from the main jet to the idle circuit. mk378 is offering valid diagnostic advice. Putting something in the gas will NOT solve the problem, the restriction needs to be physically removed. Another thing that will cause this is a worn-out throttle shaft, which is a common problem on this engine when it gets old. Check the throttle shaft for excessive looseness in the carb body.
Last edited:
Originally Posted By: wag123
Another thing that will cause this is a worn-out throttle shaft, which is a common problem on this engine when it gets old. Check the throttle shaft for excessive looseness in the carb body.
+1
I have seen this on a number of older Briggs engines, especially the vertical shaft ones. I had an engine with a throttle shaft that had so much play it would barely start. Unfortunately, a new carburetor for some of these older engines can be very expensive and difficult to source. My customer's engine was so old the part was obsolete, so I sourced a used carburetor off ebay that had low hours and no play, and was able to rebuild it.
Another thing that will cause this is a worn-out throttle shaft, which is a common problem on this engine when it gets old. Check the throttle shaft for excessive looseness in the carb body.
+1
I have seen this on a number of older Briggs engines, especially the vertical shaft ones. I had an engine with a throttle shaft that had so much play it would barely start. Unfortunately, a new carburetor for some of these older engines can be very expensive and difficult to source. My customer's engine was so old the part was obsolete, so I sourced a used carburetor off ebay that had low hours and no play, and was able to rebuild it.
Originally Posted By: jeepman3071
Originally Posted By: wag123
Another thing that will cause this is a worn-out throttle shaft, which is a common problem on this engine when it gets old. Check the throttle shaft for excessive looseness in the carb body.
+1
I have seen this on a number of older Briggs engines, especially the vertical shaft ones. I had an engine with a throttle shaft that had so much play it would barely start. Unfortunately, a new carburetor for some of these older engines can be very expensive and difficult to source. My customer's engine was so old the part was obsolete, so I sourced a used carburetor off ebay that had low hours and no play, and was able to rebuild it.
The way that I repair these is to drill the carb, press in a brass valve guide, cut it flush, ream it, and install a new throttle shaft. To do this repair you need a drill press and a B&S valve guide repair kit (something that B&S dealers were required to have in the old days). Try it jeepman.
Originally Posted By: wag123
Another thing that will cause this is a worn-out throttle shaft, which is a common problem on this engine when it gets old. Check the throttle shaft for excessive looseness in the carb body.
+1
I have seen this on a number of older Briggs engines, especially the vertical shaft ones. I had an engine with a throttle shaft that had so much play it would barely start. Unfortunately, a new carburetor for some of these older engines can be very expensive and difficult to source. My customer's engine was so old the part was obsolete, so I sourced a used carburetor off ebay that had low hours and no play, and was able to rebuild it.
The way that I repair these is to drill the carb, press in a brass valve guide, cut it flush, ream it, and install a new throttle shaft. To do this repair you need a drill press and a B&S valve guide repair kit (something that B&S dealers were required to have in the old days). Try it jeepman.
Last edited:
Originally Posted By: wag123
Originally Posted By: jeepman3071
Originally Posted By: wag123
Another thing that will cause this is a worn-out throttle shaft, which is a common problem on this engine when it gets old. Check the throttle shaft for excessive looseness in the carb body.
+1
I have seen this on a number of older Briggs engines, especially the vertical shaft ones. I had an engine with a throttle shaft that had so much play it would barely start. Unfortunately, a new carburetor for some of these older engines can be very expensive and difficult to source. My customer's engine was so old the part was obsolete, so I sourced a used carburetor off ebay that had low hours and no play, and was able to rebuild it.
The way that I repair these is to drill the carb, press in a brass valve guide, cut it flush, ream it, and install a new throttle shaft. To do this repair you need a drill press and a B&S valve guide repair kit (something that B&S dealers were required to have in the old days). Try it jeepman.
Nice, thanks for the tip! I have a drill press. Next time I run across this I will try that.
Originally Posted By: jeepman3071
Originally Posted By: wag123
Another thing that will cause this is a worn-out throttle shaft, which is a common problem on this engine when it gets old. Check the throttle shaft for excessive looseness in the carb body.
+1
I have seen this on a number of older Briggs engines, especially the vertical shaft ones. I had an engine with a throttle shaft that had so much play it would barely start. Unfortunately, a new carburetor for some of these older engines can be very expensive and difficult to source. My customer's engine was so old the part was obsolete, so I sourced a used carburetor off ebay that had low hours and no play, and was able to rebuild it.
The way that I repair these is to drill the carb, press in a brass valve guide, cut it flush, ream it, and install a new throttle shaft. To do this repair you need a drill press and a B&S valve guide repair kit (something that B&S dealers were required to have in the old days). Try it jeepman.
Nice, thanks for the tip! I have a drill press. Next time I run across this I will try that.
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