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Briggs 5.5hp engine surge

22309 Views 6 Replies 4 Participants Last post by  ZoneIII
Hello all -

I have a Briggs 5.5hp engine on my Rototiller (Model 137202-1134-E1)
I have just finished putting all new gaskets and a diaphragm on the carb after cleaning it.

The problem is that it surges up and down and the rpm's don't seem to be very high. It stays running no problem other than the surge. And as soon as I pull the throttle back a little it dies. I can see the linkage move that is connected to the governor when it does this "surge".

Also, in case this is related. The throttle lever moves very easily so I have to hold it with a bungee cord in the full throttle position.

Any advise would be greatly appreciated.
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Did it have this problem before you cleaned the carburetor?
Yes. It did this last year when I used it last. I made the mistake of leaving gas in it without stabilizer/treatment so this year when I went to fire it up it wouldn't start. The diaphragm was shot so I pulled everything off and cleaned the carb and replaced the diaphragm and gaskets. Now it will start right up but has this surge issue and won't idle down. I suspect what ever holds the throttle lever in any position is part of my problem. I can flick the lever back and forth as it just rattles around with nothing holding it in position. All the linkages and connections seem to be correct.

Last night I went ahead and tilled my garden and noticed the surge goes away while under load tilling but comes back as soon as I stop. It did stall once but it may have just been low on gas. It had some gas in it but after I filled it completely it stayed running.

Thanks for any help.
On the right side of the carburator there is a screw with a spring, it is the fuel air mixture needle.

Start the engine and let it idle until it warms up, make the adjustments at idle. Turn the mixture needle in slowly until the engine starts to idle rough and make a mental note where it's at.

Turn the mixture needle out slowly until the engine smooths out, keep turning until the engine idles rough again, then turn the mixture needle to the middle of the two positions and check acceleration by giving it full throttle. If it revs smoothly and runs smoothly your done, congratulations you adjusted your carburater.

Is the throttle lever located on the engine or the handle bar?
There is no visible fuel air mixture needle on this carb. This is a pulsa-jet carb as shown in the below link. The only visible screw with a spring is the idle speed screw. Is the fuel air mixture screw under the welch plug or is that just a mixing well? They show everything in great detail in that link including the fuel air screw but they don't show where it is located.

The throttle is located on the engine not the handle bar.

Disassembly of Briggs and Stratton Tank-mounted Pulsa-jet Fixed-jet Small Well Carburetor - Horizontal Crankshaft Engine

Thanks for the help!
Just below the welch plug slightly to the left is the fuel air mixture needle. In the link you provided the top left picture shows it. It is easier to see if you enlarge the picture by clicking on the picture. It shows as a straight/slotted screw.

That style throttle should have a big rivet holding the levers and as a pivot point. If you take the assembly off and prop the bottom side of the rivet on something solid you can tap it with a hammer and tighten it up. That should stop the lever from vibrating open or closed.
I know this thread is old but someone may still this information as these carbs are still in production. Jrrdw mentions that the idle mixture screw is present. It is in the linked pictures but it is not present on many carbs of this type. There is a screw there, in that case, but it is not adjustable. It should be screwed in all the way. There is no pointed needle end on it. It has just a blunt, flat end. So if you remove that screw and find that it has no adjustment, know that that's normal with some of these carbs. I've seen where this causes confusion when someone says that's the adjustment screw, not knowing that not all of these carbs have that adjustment.
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