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Briggs & Stratton Updraft Carburetors


JimH

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Rod, Can I assume that the wetness I am seeing at the air intake is part of the normal operation of the carb? Or do I possibly have something else going on? Or, could it be final adjustment on the high speed idle mixture screw? Although, the motor does run good, no black smoke, good idle and high throttle. Thank's, Jim.....
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Jim, to me it sounds just like normal operation. This is especially true if it runs good. Many of these carbs (I have one now) will leak a little. The leak is much less than the fuel needed to run the engine, so it doesn't affect engine operation. It will show up and even drip from the carb when sitting. I just turn off the fuel from the tank so that all the fuel doesn't leak out. My engine runs fine.
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Rod and others, thank's again for all your inputs. I guess we can say my problem is solved. By the way, I accidently ended up giving the carburetor the "overnight" leak test. Forgot to shut gas off at tank after running tractor. And to my surprise, "NO LEAKING" I'm happy............... Jim...............
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quote:
Originally posted by JimH
Rod and others, thank's again for all your inputs. I guess we can say my problem is solved. By the way, I accidently ended up giving the carburetor the "overnight" leak test. Forgot to shut gas off at tank after running tractor. And to my surprise, "NO LEAKING" I'm happy............... Jim...............
Final update to my last post. As I had stated in an earlier post, I found the upper carb body to be warped on the side where there is no screw. (common prob for the 3-bolt carbs) I THOUGHT I had that issue temporarily resolved! WRONG! I ended up doing some "creative" filing on the upper carb body to try to off-set the warpage. Along with doing that, I used 2 gaskets between the upper and lower bodies. Problem finally resolved this time. Hope this helps others with similar problems.
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Just a thought... when modding an engine, if the gas tank is raised/carb lowered, the gas pressure from the tank can increase to the point of over-riding the pressure created by the float on the needle/seat, and cause the carb bowl to overflow... bob
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It would have to be a dramatic change, or you would have to have a carb that was already marginally sealing. Most carbs will seal well above the pressure exerted by gravity flow fuel systems, even if the tank is directly above the carb. I have even seen electric fuel pump conversions that use the stock needle and seat with great success. However, if your carb was barely sealing to begin with, then you would have a problem.
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Many owners of Simplicity Power-Max's and their Allis equivalents have converted to electrical fuel pumps with great success. No problems with fuel leaking past the needle and seat. (at least not that I'm aware of) The leaking I was getting was not from the needle and seat. It was from the upper body being warped, thus causing extra fuel to spill in the carb along with seepage outside the carb with the motor running. I had no dripping with the motor off and the fuel turned on. By filing the upper carb body and using 2 gaskets between the upper and lower bodies, my problem was resolved.
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You don't have to worry much about lowering a carb. Each inch will only add about 0.026 psi. That may not be exact, I just did a quick calculation to see what a ballpark number was.
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  • 2 weeks later...
Anyone have problems with an electrical pump having too much pressure and pumping fuel into the crankcase through the fuel pump that is built into the carb on the twin B&S engines? bob
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Looking at Rods drawing I thought of a small o-ring readily available at any hardware plumbing dept. the nylon washer is also a great idea, anyone think the gas would adversly affect the rubber o-ring?
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You need to check compatibility of the o-ring material with gasoline. I am pretty sure that butyl rubber is not compatible, but I think neoprene is. Parker Corporation makes o-rings from many different materials. If you can get hold of one of their catalogs, they usually have the compatibility charts included.
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  • 1 month later...
Im really glad i read this post. Can anyone confirm that the emulsion tube comes with the Briggs carb rebuild kit? If not where do i get one. Mine was about 1" long when i took the carb apart and went nowhere it just stopped in the middle of the venture. No wonder this thing barely ran when i parked it a few years ago.
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Any time I have ordered a complete rebuild kit it had a new emulsion tube. You can also order the tube separate. Jack's small engine warehouse has a good supply of briggs carb parts.
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The Girls Can Flirt And Other Queer Things Can Do. A memnonic for the Moh's hardness scale: Talc, Gypsum, Flourospar, Apatite, Quartz, Topaz, Corundum (Ruby), Diamond. Dark's response on Nov. 13th prompted my response. I had no idea that talc was hard enough to use for this operation.
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