Mower Trouble

mx_spaceaceMay 16, 2010

I have a early 90's Roper BST300AR Lawn Keeper. This is also referred to as either an AYP or Sears.

It is a 20" front wheel drive self propelled mower with a Tecumseh 3.5 motor.

I cannot get the motor to "Run" it will start up for a moment, even get to high RPM but as soon as it empties the primer it dies.

Spraying starting fluid in gives same result, starts up but almost immediately dies off. i get only about 5 seconds of run time.

I have changed oil, spark plug, air filter, fuel line, fresh fuel, cleaned carburetor (best I can), I have checked the dead man cable and all seems to be fine.

If anyone has any suggestions I would love to hear them.


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You can add some "Gum-out" or similar fuel system cleaner to the gas, start the mower, and keep it running with the primer button. There is a reasonable chance that after 5 or 10 minutes of operation, it will run without the primer. There might be varnish in the carburetor, hidden someplace that you were unable to clean. There is no guarantee that this will work, but its worth a try.

    Bookmark   May 16, 2010 at 5:45PM
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What Eric said. I 've had mixed success with this or just keeping the engine running with squirts of carb cleaner down the throat of the carb. Worth a shot, though..

    Bookmark   May 16, 2010 at 6:34PM
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I'll get a second person to assist, i have tried to spray as soon as started but it usually quits even before i can ger around the handle bar to add more spray.

Any other Thoughts?

    Bookmark   May 16, 2010 at 9:31PM
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Maybe a Briggs engine?

    Bookmark   May 16, 2010 at 11:26PM
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yeah, really, never had this much trouble with a Briggs.

Update: tried keeping it running with spraying starter fluid in, could not keep it running. it would start, peak, and die.

    Bookmark   May 16, 2010 at 11:40PM
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That was my question. Are you sure it's not a Briggs engine? If so, the diaphragm on your tank mounted carb is shot. The ethanol fuel is causing many to fail prematurely. Choose a fuel like Gulf and maybe Shell that doesn't use ethanol.

    Bookmark   May 17, 2010 at 6:09AM
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I have a craftsman 6.75 HP, self propelled and took the thing apart to change the oil seals. Putting it back, I washed I have before..but this time, I can't get the thing to start. Here's where it is weird..The bar you hold to start it, when I let it go, the thing I tear is back down to look at is normal..i ohmed the wires with it opened and closed..normal..what am I missing on this??

    Bookmark   May 17, 2010 at 9:34AM
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With the bar pulled in, there should be an open switch or infinite ohms. Where, in the bar's movement, does the switch close?

    Bookmark   May 17, 2010 at 11:19AM
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It is a Tecumseh Motor. TVS90.
I have never used an ethanol added fuel in this or any of my lawn/garden motors. Only 87 Octane Unleaded.
The carburetor is mounted to the motor on the opposite side from the fuel tank and has a brand new 20"ish long 1/4" fuel line... no fuel filter currently or prior.
The primer bulb does seem to be sucking fuel from the tank albeit slow, there are no holes or splits in the primer bulb.
When the tank had fuel in it, and the line removed from the carburater Fuel was flowing freely all over my bench. (No Smoking Please)

    Bookmark   May 17, 2010 at 4:48PM
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I have found it not uncommon that those carbs don't fill unless the tank is full or you actually cup your mouth over the tank opening and force the gas into the carb. I've taken the bowl nuts out, bounced the wheels and still no gas flow. For some reason, once the bowl is full, you won't have a problem again until it goes empty.

You might want to check the small orifices in the jet.

Shown are 3 of the typical jets and the small holes. All 3 are Tecumseh jets. Briggs jets are similar with the center-bottom hole and one on the side. All these holes need to be fully clean and open for the engine to run correctly.
Some jets only have the center-bottom hole.

    Bookmark   May 17, 2010 at 8:16PM
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