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Leaking B&S carb

sod's Avatar

Join Date: May 2004
Posts: 88

08-01-07, 08:46 AM   #1  
Leaking B&S carb

Carb leaks into air filter housing after shut down. Repalced the needle and seat same problem. Borrowed a neighbor's carb off the same Toro Recycler model 20023 mower. On his mower he has no leak back problem. Put his carb on my mower and sure enough the carb leaks into the air filter after it sits for a while when the engine is shut down.

Any ideas as to the cause and the fix would be very much appreciated. Thanks

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jsouth's Avatar

Join Date: Jul 2005
Posts: 205

08-01-07, 12:35 PM   #2  
Just a guess replace the gas cap see what happens,with your neighbor mower if they are the same,maybe building pressure in the gas tank.


repair_guy's Avatar
New Member

Join Date: Apr 2004
Posts: 539

08-01-07, 12:42 PM   #3  
Did you check the float.If it has a hole in it it's allowing gas to enter and this weighs it down where it doesn't come up to let the inlet needle close.
Take it out and shake it,you'll be able to hear the gas sloshing around.

30yearTech's Avatar

Join Date: Oct 2006
Posts: 1,176

08-01-07, 06:49 PM   #4  
My guess would be a plugged carburetor vent.

These carburetors are vented through the primer assembly.

Since you installed your neighbors carburetor and it leaked on your mower but I assume (lol) that it was not leaking on his.

If you installed your air filter assembly then I would suspect a restriction in the carburetor bowl vent. If air cannot easily enter the float bowl then when fuel flows into the carburetor, pressure is built up inside the float bowl. This pressure can hold the float down and cause the carburetor to leak gas.

If the venting is restricted in your primer assembly, then any carburetor you put on your engine will also leak fuel.

It's the only thing I can think that would cause this.


Join Date: Mar 2007
Posts: 354

08-02-07, 08:01 AM   #5  
You stated that you borrowed the carb off a neighbors same model mower and his did not leak until it was placed on your mower leads to believe that your gas cap is not properly venting. As a service tech for a Toro shop with over 50 years experience, previous statements that these carbs vent through the primer are correct, but the tank needs to vent also. If you build up pressure in the fuel tank it has to go somewhere and if it can not vent the air on top of the fuel in the tank it will build pressure up in the tank forcing fuel into the carb causing the weeping of gas. Replace the fuel cap with the proper cap from Briggs or Toro. When you put the carb back on the neighbors watch where the air cleaner housing plate attaches to the carb. The gasket must be in good shape or the carb will not prime causing hard starting, especially when the temperatures are lower. You should see a good fuel stream when you push on the primer and looking in the carb thoat.

sod's Avatar

Join Date: May 2004
Posts: 88

08-02-07, 01:12 PM   #6  
Thanks everyone for your replies

I will check the carb vent to make sure it is not plugged. Also, get a new gas cap if the vent is ok. I will let you know how it goes.

P.S. I live in the Twin Cities and right now my mower problem seems so very minor compared to the situation less than five miles from our home where the 35W bridge collapsed last night. What a terrible tragedy.

sod's Avatar

Join Date: May 2004
Posts: 88

08-06-07, 08:08 PM   #7  
Problem fixed

Thanks to the help provided here, my mower's carb leaking problem is now history. The fix was a new gas cap. Thanks everyone.

wmswilson1's Avatar

Join Date: Aug 2008
Posts: 5

08-27-08, 02:09 PM   #8  
thank you some much i had a the same problem and it stopped my leak too!!!!!!!!

Larrytigermt's Avatar

Join Date: May 2013
Posts: 1

05-20-13, 07:58 PM   #9  
Same problem. Gas is leaking into air filter housing.

The little red tube that should be sticking out of the carborator is missing. Is this what is makinging it leak? It was running okay with out it but now it runs for a while then runs rough then dies. Any thoughts? Thanks.

cheese's Avatar
Forum Topic Moderator

Join Date: Jul 2001
Posts: 16,574

05-20-13, 08:21 PM   #10  
A red tube in a briggs carb? Same model as the one this thread is about?

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