Briggs and Stratton 4.5 horse surging

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ls1mike

$50 Site Donor 2026
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Hey All,

Rebuilt the carb in my 4.5 Briggs. It is better but it still runs rough and will surge. New plug, filter, carb kit (gasket, diaphragm, spring and sock) New premium gas.

Any ides
 
How is the fuel line/hose from the tank to the carb? I had one before that looked pretty decent on the outside (save for a few little cracks on the rubber), but was collapsed on the inside and I had the same symptoms.
 
Hmmm, didn't check that. I guess that is really all that is left as the governor and the arm that controls it seem to be working fine.

I will take a look! Thanks!
 
No problem. Even upon inspection, the hose looked fine in my case. I had to put vacuum to it to actually see it collapse. I think I just had a spare hose lying around that I cut to length, and that did it. As in your case, everything else seemed A-ok.
 
Originally Posted By: Klutch9
No problem. Even upon inspection, the hose looked fine in my case. I had to put vacuum to it to actually see it collapse. I think I just had a spare hose lying around that I cut to length, and that did it. As in your case, everything else seemed A-ok.


So I went out there and looked...I forgot the carb is right on the tank. It has one small rubber elbow from the carb to a metal tube which leads into the combustion chamber. The elbow does not collapse.
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Thanks!
 
Originally Posted By: ls1mike
11A 414E729 was the model number

It also had the following 407 896


That's the model number of the mower. Do you see any numbers on the engine anywhere ?
 
Originally Posted By: ls1mike
That is the one. Thanks!


Ok I've worked on that one. The neighbor next door has one on her Craftsman mower. At the bottom of the page in that link is that blue plastic main nozzle. The way you remove that is by pulling out the throttle plate first and then pulling out the throttle shaft. The throttle plate pulls out easy with nose pliers. After that, you can stick a flat blade screwdriver down in the venturi and push the main nozzle out from the inside. After you get the main nozzle out, then you can check to see if the holes in it are clear and also check the condition of the O-ring. If the holes are blocked, the engine will run lean. If the O-ring is old and dry, that will cause fuel to leak past it causing the engine to run rich. Either of those two conditions will cause surging. You also should check the condition of the primer bulb. If it's old and dry, it might be cracked. A cracked primer bulb will suck in air and cause the engine to run lean. And besides that, you have to remove the primer bulb to replace the primer check valve anyway.
 
Originally Posted By: bubbatime
If you cant figure it out after fiddling with it, just replace the carb. They are only like $20 on eBay.

Well after reading the repair procedure. I went onto ebay and pruchased an OEM carb for 20 bucks shipped. Thanks for the tip! Well worth it as I like this mower because it is light and is a bagger. I have a much newer Troy Bilt 675 series bagger self propelled, but I just don't like self propelled push mowers.
 
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