Briggs Intek V Twin surging

[tnt_motorsports]

Almost certainly a carburetor issue if it clears up by dribbling fuel or with the choke. You are manually overcoming the lack of fuel. Take the carburetor off and soak it in carburetor cleaner. I like the B-12. Blow the passages out with air and see if that helps.

just my $0.02

 

[Avery4]

Almost certainly a carburetor issue if it clears up by dribbling fuel or with the choke. You are manually overcoming the lack of fuel. Take the carburetor off and soak it in carburetor cleaner. I like the B-12. Blow the passages out with air and see if that helps.

just my $0.02

That's pretty much what I thought, thank you for confirming. I just find it odd that the carburetor looked so clean and I wasn't able to get it to work properly even after cleaning it several times. I spent the better part of this afternoon and almost a whole can of brake cleaner cleaning the carb several times with no luck. I will try cleaning it one more time tomorrow and if it still doesn't run right it's getting a new carb and I will report back with the results either way.

 

[supton]

If it doesn't surge while the engine is under load (mowing) it's almost 100% a low speed/idle jet.

Mine is doing that, and I’m hoping that there is an idle screw on it—maybe I will get lucky and it will respond…

[I goofed and left the gas cap off… and it rained… so I know water went through the thing. Drained and it mows good, but hunts when not loaded.]

 

[thastinger]

99.8% of the time surging is caused by a lean fuel mixture, the "surging" is just the governor attempting to regulate the RPMs.
Since you say it does it at all RPMs, I would search for an air leak where the engine is bringing in unregulated air downstream of the carb. The twin cylinder motors sometimes develop leaks where the intake manifold bolts to the cylinder heads, I would check there.

 

[Avery4]

99.8% of the time surging is caused by a lean fuel mixture, the "surging" is just the governor attempting to regulate the RPMs.
Since you say it does it at all RPMs, I would search for an air leak where the engine is bringing in unregulated air downstream of the carb. The twin cylinder motors sometimes develop leaks where the intake manifold bolts to the cylinder heads, I would check there.

That's a great point, the plastic intake manifold was one of my first suspects. It appears to be sealed though, I sprayed brake cleaner around the whole thing.

 

[Avery4]

Well I guess 4th time is the charm, after the 4th time cleaning the carb it finally runs properly. I didn't see any chunks come out of the carb, but as several people said it doesn't take much to clog it.

I also discovered a second problem- the tube that goes from the valve cover to the fuel pump had a crack in it where it pushes into the valve cover. I'm not sure how much that was affecting the pump's operation since it seemed to run properly after cleaning the carb for the 4th time, but it was definitely going to become a problem when it eventually broke off off so I'm glad I found it and got it fixed.

Thanks again for your help everyone!

 

[Lubener]

Great suggestion. I think there is more to the problem than the governor though because I tried manually holding the throttle at a steady position and although the RPM stabilized, the engine still didn't run smoothly. The only thing that smooths it out is dribbling fuel into the carb or setting the choke just right. There are no air leaks, I sprayed brake cleaner around the carb and intake manifold to check for vacuum leaks and nothing changed.

Don't mess with the governor. It is not your problem. You answered your question when you stated about having to add fuel or partially choking it. Your engine is running too lean. Check your fuel delivery or for air leaks.

 

[Avery4]

As I said above, I finally got it to run properly after cleaning the carburetor for the 4th time. Thanks for your help!

 

[danez_yoda]

Just because its working now doesn't mean its fixed. Youll get comments for the next 10 years on how to fix that carb.

On some sites you can change the title to include (SOVLED) to save peoples time.

Glad you solved the problem with your carb.

 

[wag123]

There isn't anything wrong with the governor or the spring. It is working the way it is supposed to work. Leave it alone.
You have a restriction in the carburetor's idle circuit, there is a bit of dirt/debris/varnish caught in the idle circuit jet. 99% of the time dumping something in the gas (like Seafoam or B12) won't cure this problem. The dirt/debris/varnish needs to be physically removed. The carburetor needs to be removed and disassembled so you can physically poke through all of the jet holes with a small stiff steel wire (I have always used the wire inside plastic twist ties). Then you need to spray carb cleaner through all of the holes and passages to make sure they are clear. I have done thousands of them, this will solve the problem.

 

[mk378]

Use carb cleaner for best results, its much more powerful solvent than brake cleaner.

On these the idle circuit goes up top under the metal plate on the top of the carb. Plate should be removed for a thorough cleaning.

To tell if you have an idle circuit problem pull the thottle rod linkage (on the carburetor throttle plate) all the way closed, the engine should run slow and smooth. Sometimes just turning the mechanical stop screw on the plate lever up a little will cure surging with no load.

 

[oil pan 4]

My intek mower started doing that for the first time. I figured it was a misfire, replaced a plug and it was back to normal.