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pullgear

updraft carb leak

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pullgear
I need help with the Briggs updraft carb. I must be missing something, I have taken this thing apart and played with the float height one dozen times. Is it still not clean? Please give advice to cleaning techniques and help dialing these things in. Thanks Scott.

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HubbardRA
There are two leakage paths in the updraft carb. One is through the needlevalve, but the other is a leakage at the emusion tube seat. Both can be seen in the attached picture. Green line is a needlevalve leak, and blue is a leak at the tube seat.


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JJ MARSHALL
try shaking the float and see if maybe it full of gas. i have found the float to have a small hole in it and gas would get in side it . which would make it heavy and it would not cut the fuel off . JJ

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HubbardRA
Roy, I was talking about the float needle valve, not the jet adjustment needles. If the float needle does not seal off, the fuel will completely fill the cavity and leak as shown by the green line and stated in the last sentence of Maynard's post. Another good reason to remain quiet and not try to help other people. Always critics in the bunch.

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briggsetc
I have been studying and rebuilding the flo jets for a while now. Beautiful carb but you can't trust them not to leak. That is why I always test run them on a motor I have set up just for carb testing. Before selling one. Totaly agree with leaks at the float seat shown in green. Just to clear up any confusion there might be.... I didn't think there was a seat right at the bottom of the power jet/emulsion tube [red arrow] and checked a carb to verify that. The actual leak occurs at the highest point of the blue line. I have tried a few things to fix the seat but have not had good results yet. The most promising idea is to modify an old tube to act as a tool to lap in the seat. I have a few hours invested with bare float bowls set in a vice with the tube in, filled to level with gas, to try different things. Seems simple enough to stop the leak..NOT. Gary

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UCD
Rod I modified my Diagram and wording that you copied and only posted part of to correctly state the high and low speed needles are not the reason for a dripping carb but the power jet seat/emulsion tube or the float needle and seat are. Roy "Always critics in the bunch." That remark applies as much to you as anyone else. People in glass houses should't throw stones.

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HubbardRA
Maynard, I did not copy only part of your picture. The picture I posted was from a post someone made many years ago and I have kept in my archives for just such questions. If you created the picture, then there were no words on it when I got it. You are alluding that I used your picture and deliberately removed the explanatory sentences. What would be the purpose of that? I was just trying to show that there were two distinct leakage paths. By the way, I was not throwing stones, just dodging the ones that had been thrown at me.

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UCD
Rod I was not throwing any stones at you either, (someone else implied that) I just posted the complete diagram that I had made up several years ago from a carb drawing I found in I believe a Briggs manual. In the original I meant the high and low speed needles/jets not the float needle & seat. Yes it did need clarifying. The remarks were not called for.

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RHA
My 2 cents worth,I read a possible fix if the gas was leaking by the seat-float needle, was to put valve grinding compound on the float needle and use your fingers to spin the float needle against its seat to insure a good sealdOd. Then clean the seat and needle with carb cleaner!!! Not that I know alot about it,but that made good sense to me!

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Storm7012
I've rebuilt a few of these now. My biggest problem has always been setting the float. Dead level isn't always the way it needs to be. Seems like each carb is just a bit different. I've only did around eight now, but the first couple was off and apart a dozen times before I got it right. Oh, some just always seem to drip just a little no matter what I've done.

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toomanytractors
I've had good luck cleaning the needle valve seat and the seat for the emulsion tube by putting a small amount of white polishing compound on a Q-tip and rotating it on the seat. Blow out with air and spray with carb cleaner when done. I would be hesitant about valve grinding compound as it is far more abrasive and was intended for use on much harder metals than either the needle valves or seats.

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JimH
quote:
Originally posted by pullgear
I need help with the Briggs updraft carb. I must be missing something, I have taken this thing apart and played with the float height one dozen times. Is it still not clean? Please give advice to cleaning techniques and help dialing these things in. Thanks Scott.
Scott, another thing to check is that if you have the carb with 3 screws that hold the top to the bowl, they are notorious for warpage where the 2 halves meet. If a .002" shim can be inserted between gasket and halves, that is too much. I have been successful doing some "creative filing" on the top half and using 2 gaskets to stop leakage there. If you have the 4-screw type, warpage should not an issue. Good luck and keep us posted.

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