SOLVED! Gas Leaks on Lawn Mowers

This video covers: How to Diagnose and Fix lawn mower fuel leaks.

How To Clean the Carburetor:


5 Different Common Fuel Leaks on small engine lawn mower carburetors discussed and solutions offered. How to diagnose and treat these issues.
*** 1 MORE! Check the float for fluid trapped inside. This one is sneaky because it can take over night to illustrate. Tecumseh usually has more issues here with brass floats being punctured.



44 thoughts on “SOLVED! Gas Leaks on Lawn Mowers

  1. Thanks for a detailed video. My float was full of fuel. Didnt even know anything about lawn mower engines before this video. Shop wanted $80 plus parts.

  2. Thanks for the info! On a Tecumseh 3 HP vertical shaft ice auger, With a diaphragm carburetor. When I lay it down for a while and then pick it back up vertically it leaks fuel out of the exhaust . What would cause this?

  3. Awesome video, if after all of that the Carb still leaks, than its the float. Replace the float and make sure the open end of the needle clip is put in right. Open pointy end facing the choke .

  4. gas is leaking from the air hole on the prime button. It is just sitting there leaking without me touching it. I have lost a whole tank of gas in less than a day. What causes this?
     I thought there was a tear or crack in the button so I replaced it yesterday. No difference….still leaking.

  5. is there any reason after putting the carburetor back on that gas would leak out of the green gasket that is between the carburetor and the plastic piece that connects to the engine. when priming there is no resistance. all I hear is air unit gas comes out. The green gasket has been replace but still its leaking. the carburetor has a channel or canal that I believe the gas is coming out of. I believe its for venting.. Let me know what you think. thank you. 

  6. don't forget a saturated float ( pinholes )metal float will leave the fuel system wide open to overflow, will flow out the choke. I find this the most common.

  7. Hi Adam.  Just watched your "solving carb gas leaks" video.  I found it informative and easy to understand…After cleaning my Tecumseh carb (it has an adjustable main fuel jet, bowl bottom drain, adjustable idle mixture and idle speed screw), I installed a new valve seat and float valve needle.  When remounted to my 1967 7hp YardMan Snow Bird Snow Thrower, gas still leaks out of the choke opening. No float level adjustments were deemed necessary during dis-assembly as the float held a slightly-above horizontal position when the carb was held in hand up-side-down.  I had a similar gas leak problem once before with a 1986 5hp Tecumseh engine whose primer bulb had lost it vent to atmosphere – boy, that was an elusive problem to solve! – but this engine has a rather rudimentary primer, which consists of a small plate attached to the end of a spring-loaded plunger, which when pushed in, simply closes loosely against the carb throat.  I carefully inspected the float to be sure that the exterior was without varnish build-up, that there was no fuel in it, and the float needle spring clip's open end is facing the choke side of the carb. I also checked to be sure that the gas tank is vented to atmosphere as well.  Do you have any suggestions?  Thank you.  PA

  8. Thanks for this video I was so close to throwing out the lawn mower that came with our new house because of a gas leak and thanks to your video I found out it was from needle and seat and I was able to fix it thanks again

  9. I've been working on my 16 year old Briggs & S a good 10 to 12 hours or so, my first time! Did everything perfect! (I thought) Learned all I know threw YouTube on this project. Rebuilt the carb, paint and all! Was all done. Thing looked bran new! Put gas in the tank, and it leaked like Feak'n Crazy! I was totally gonna trash my 10 hours of work and over 120 bucks I had put into this project and chuck it in the street for the next guy to deal with. I couldn't understand why it was leaking for the life of me! Then Came your Video. Thanks Adam. I didn't seat the toilet bowl needle thing-a-ma-bob! It's now Dry as the Valley I live in! Now to repaint this peeled gas saturated thing… Oh Well, Thanks again.

  10. My carb on my Honda hrr216 was leaking gas so I replaced it with a new one with . I put the new one on and it still is running gas down carburator. Can't find the leak still. Any thoughts? Thanks bud

  11. #5 was the culprit for me. Showing and explaining the tools was a huge help. I was able to use one of my wife's smaller knitting needles to remove the pin seat and a thin rod with some electric tape wound around it just off the tip (sort of replicating what you had there) to properly position the replacement pin seat. Thanks!

  12. Thanks for the video, just what i needed! I pulled the B&S carburetor off and opened it up, the float had dried on material, cleaned it up and the mower runs like a charm!

  13. Thank you for sharing your knowledge with those of us who are mechanically challenged. I found your video thorough, informative, and easy to understand.

  14. mine was leaking gas all over the place , took gas out of tank ,took apart to get a look at the carb, poured gas in and not leaking , put everything back together and running fine. started it up once every hour for 5 hours and no leaks. question , why did it only leak that one time and what would be the most common thing for this to happen, would like your opinion adam. by the way, great video MAN!!!

  15. I have a husqvarna riding mower, I've cleaned up the carb and now i see gas spitting out the muffler under the motor. i need help!!! can someone please explain why please.

  16. I just found my Sears YT3000 riding mower on my driveway covered with gas(the deck, etc.) It doesn't appear to be leaking around the fuel filter or from the fuel line. The concrete pavement under and around the mower was flooded with gas, as well(not just a little drip!) I had put gas in it a few days ago, but did not crank it. I'm assuming that since nearly ALL of the fuel has leaked out of the plastic tank, it must be a crack or leak in the tank somewhere(or maybe a bolt underneath the tank that connects it somehow?)
    Are these plastic gas tanks expensive/difficult to replace? Can they be repaired? Any other ideas? I live in a VERY hot, humid southern state…and the mower sits out in the sun.
    Thanks so much for your videos. They are very helpful for a single woman with minimal skills to follow!

  17. In the last example (needle seat), the gas on the B&S will be running out of the center hole on the prime bulb. B&S Needle & Seat is #398188.

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