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Push Mower Runs, But Not Well


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#1 whitelt120 OFFLINE  

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Posted October 12, 2012 - 09:03 AM

today me and a couple of kids were working on one of our teachers push mowers in ag class. We can get it to start right up, but it sputters like crazy. I tipped it back while it was running and it stop sputtering. All of a sudden it started running like a champ so I sat it back down, and wouldn't you know it it started suttering again. I was hoping someone could help us we cannot figure it out!
Thanks for the help!

The push mower has a 4.00 briggs and stratton engine

#2 Kyocum OFFLINE  

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Posted October 12, 2012 - 10:02 AM

It sounds to me like a float/carb issue. I would start at the carb. Prolly could use a good cleaning and rebuild.

#3 whitelt120 OFFLINE  

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Posted October 12, 2012 - 10:26 AM

My teacher told us he had cleaned it. It is a pulsa jet plastic carb model it doesn t have a float I believe

#4 MH81 ONLINE  

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Posted October 12, 2012 - 11:11 AM

I would clean out the gas tank & put in fresh gas. Sounds like a layer of water in the bottom near the carb pickup...
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#5 dave8338 OFFLINE  

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Posted October 12, 2012 - 01:51 PM

Not sure I've heard of a pulse carb on anything other than a two stroke machine. Do you have any pictures?

Usually when an engine smooths out while running at a grade, it is float related and "usually" is a result of an improper float height, as mentioned. Could be water in the float bowl as it settles to the bottom and when tipped back, would run to the back of the float bowl, away from the emulsion tube for the main jet passage.

Edited by dave8338, October 12, 2012 - 01:51 PM.


#6 Bmerf ONLINE  

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Posted October 12, 2012 - 02:22 PM

How old is the motor? Does it have low oil warning on it? I’ve seen the new motors with this feature sputter and die or not start at all when the oil level is barely low. When tipped up the sensor is covered and motor smooths out. Models equipped with this feature usually have a small red light that flickers on and off in unison with the stumble of the engine. Unsure of what you have, good luck.

#7 MH81 ONLINE  

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Posted October 12, 2012 - 04:13 PM

Not sure I've heard of a pulse carb on anything other than a two stroke machine. Do you have any pictures?


Most of the Briggs like that had a carb bolted on top of the tank, with no "bowl" in the classic sense. the tank was the bowl. IDK if it's a "pulse" carb, but mine has some kind of diaphragm helper pump.

Posted Image

if there was water in the bottom of the tank, it may be trying to suck it up the tube.
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#8 HDWildBill OFFLINE  

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Posted October 12, 2012 - 04:40 PM

I just fixed one with a plastic pulse jet carb. Whiteit120 is correct there is not float with this carb. I suspect your teacher did not put the diaphragm together correctly. Also I have gotten to the point with these carburetor's that it is cheaper to replace them ($26) then to try and clean them. There are 2 bolts that hole the carburetor on one on the engine block and the other on the fwd bracket. remove both bolts and pull the carburetor toward you and disconnect the linkage. The tank and carburetor will come off together. Now pull the screws that hold the base of the carburetor to the gas tank and pull it straight up. you should see a diaphragm gasket, spring and screen/filter. check the condition of the diaphragm if it is puffed out replace it. After you have made sure everything is clean, make sure that where the carb sits on the tank is clean and there are a couple of little holes that are on the tank that need to be clean, When you are happy everything is clean and in good working order put the diaphragm on the tank and line up the holes. next put the gasket on top of the diaphragm and line it up. Make sure you have the spring on the spindle on the carburetor and the screen filter are on the spout. Re-install the carburetor on to the gas tank and re-install the unit back on the engine. Oh and there is an O-Ring just inside the carburetor's outlet where it goes on the manifold, make sure it is in good nick.

Here is a youtube video so you can see better what I'm talking about. Let us know how you make out.

Opp's forgot the link.


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#9 whitelt120 OFFLINE  

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Posted November 01, 2012 - 08:38 AM

that would be it thanks so much for all of your help I really appreciate it! We will get back to work on it soon we just got back from ffa convention a few days ago. We haven t had much time to work on it lately but if all goes well we should have it up and running well by next week!

Edited by whitelt120, November 01, 2012 - 08:39 AM.


#10 1978murray OFFLINE  

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Posted November 01, 2012 - 08:41 AM

put a new diaphram in it. The new gas eats them and they go bad A LOT. also make sure that all the springs are in the right place in the carb and that the screens are all clear
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#11 whitelt120 OFFLINE  

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Posted November 02, 2012 - 08:42 AM

I will be sure to keep an eye on them them we take it apart

#12 jdslednut OFFLINE  

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Posted November 02, 2012 - 03:27 PM

Check the pick-up tube for cracks. It may be losing prime and when the engine is tipped the crack in the tube is imersed in the tank's fuel.




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