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Gene's Shop

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Carburetor Overhaul

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When I picked up the Simplicity 3012 from SimplicitySwede earlier this spring, he told me it leaked gasoline from the carburetor. He controlled the leaking while parked by shutting off the valve under the gas tank, however there was a constant drip while operating the tractor as well. My shop is in the basement of our house and, any slight smell of gasoline permeates the Linda's house. So, I either have to keep these things under control or move the culprit tractor out under the deck (for now). So last weekend I decided to overhaul the Briggs updraft carburetor on the 3012 to keep peace and harmony in the family. Had an overhaul kit on the shelf that I'd bought from Al Eden some time ago (old part number displayed) and I've done this several times so I set about the task to rebuild. This is going to be a piece of cake ;). Just to be sure I stay on task I pull out the Briggs carb adjustment cheat sheet.



No job is routine! After overhaul the tractor ran rougher than before, wouldn't throttle up or down evenly, and leaked from this hole even more than before my overhaul.



I have a back stock (Linda's term for my inventory) so I pulled the carburetor box off the shelf, got out the trusty Dremel, and cleaned up a different lower body determining this must be my problem along with maybe a float adjustment. 



After wire brushing, polishing, and compressed air, the replacement lower body was ready for service. 



Still leaked!  Back to the bench. I'd recently read an article in Lawn & Garden Tractor Magazine by Norman Ng, owner of iSaveTractors who talked about this very problem with Briggs updraft carbs. I determined the gasoline was likely leaking past the surfaces where the emulsion tube is supposed to seal against the carb lower body. In the past I've used a Q-tip and toothpaste to smooth up surfaces but I decided to follow Norman's advice placing an o-ring on the emulsion tube. Norman's article is also on his website http://isavetractors.com/articles-1/ 

Again, back stock time. I bought an o-ring kit from my local Carquest auto parts store (no longer in business) a few years ago that's come in handy to rebuild fdt hydrolifts among other things. The smallest 006 fit the tube nicely. 



I reassembled the carb adjusting per Briggs instructions with the cleaned up 2nd lower body. No leaks while setting or running!! Not only that but, after idling for a full 5 minutes and readjusting the needle valve, the old Briggs 12hp runs like a Singer sewing machine while idling, throttles up nicely and gives off only a light puff of smoke on quick throttle up. Not bad for a 50yr old motor. 


The 3012 is now parked back in our basement out of the elements. No gasoline aroma from her now however I think I will call the concrete guy this week to see what his schedule is. Maybe its time to accelerate the shop build...




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I have had similar issues with my 3112V carb, have to give this a try, thanks for posting!

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