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Fix Your Stuff

Right to Repair

Parts & Tools

Introduction

This guide takes a little more work than some of the other lawn mower replacements. You first remove the air filter, and then go behind it to remove and clean the carburetor tank. You will use a socket wrench with a 5/16" and ½" hex bit and a prying tool. Before you get started, you may want to purchase an O-ring if your lawn mower is old, as the O-ring in the carburetor tank may be worn. Cleaning the carburetor may get messy, so do not attempt it inside.

  1. Make sure the the engine is off and the spark plug wire is removed and away from the spark plug before beginning.
    • Make sure the the engine is off and the spark plug wire is removed and away from the spark plug before beginning.

    • Use a Flathead #4 screw driver to remove the 40mm screw that holds the air filter case in place.

  2. Use your hands to pull the air filter case out of the hinge at the bottom.
    • Use your hands to pull the air filter case out of the hinge at the bottom.

  3. Use a socket wrench with a 5/16" hex bit to remove three 20mm bolts behind the air filter. Use your hand to remove the plastic backing to the air filter, exposing the carburetor.
    • Use a socket wrench with a 5/16" hex bit to remove three 20mm bolts behind the air filter.

    • Use your hand to remove the plastic backing to the air filter, exposing the carburetor.

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  5. Note: There is a plastic washer that may come off when you take off the plastic backing. This is normal; just set it aside and save it for reassembly.
    • Note: There is a plastic washer that may come off when you take off the plastic backing. This is normal; just set it aside and save it for reassembly.

  6. Use a socket wrench with a ½" hex bit to remove 11mm screw on the bottom of the tank.
    • Use a socket wrench with a ½" hex bit to remove 11mm screw on the bottom of the tank.

    Make sure you empty the fuel, remove the fuel tank, or clamp the fuel line before you do this step, or you'll get fuel everywhere!

    Calion - Reply

    Yes, definitely clamp off the fuel line with locking pliers. I can’t believe this guide would neglect to mention that.

    Also, I would not call this a “tank” — it is not the fuel tank. Everybody who works on small engines calls it a fuel bowl.

    Trevor Kemp - Reply

    Mine was a 13mm on the fuel bowl..empty fuel tank first

    dslyr - Reply

  7. Once the bolt is removed from the bottom of the carburetor tank, gently pry open the tank with a metal prying spudger until it pops off. If you do not have a spudger, a flathead screwdriver will work. Completely remove the tank so you can clean it or replace it.
    • Once the bolt is removed from the bottom of the carburetor tank, gently pry open the tank with a metal prying spudger until it pops off. If you do not have a spudger, a flathead screwdriver will work.

    • Completely remove the tank so you can clean it or replace it.

    The thing that is most important to clean here is the screw in the bottom. It has holes which, if clogged, will prevent your engine from running for more than a second or two. Make sure you clean them out with carburetor cleaner. It's easy to miss, as it falls out into the socket when it's unscrewed.

    Calion - Reply

    Calion

    Your old post on cleaning the float bowl retaining nut was a real problem solver for me. Had done everything but clean n the flow thru holes in the retaining nut. Reassembled and mower engine started right up. Thanks a lot. Sam

    Samuell Gonzales - Reply

    Yes, definitely need to clean out the ports in the bolt with a needle, can’t believe that’s not included in a guide about maintaining a carburetor.

    Similar comment to previous step, it’s a fuel bowl, not a fuel tank.

    Trevor Kemp - Reply

    What is the purpose of the bolt with the hole .

    dslyr - Reply

  8. Inspect the O-ring inside the carburetor tank. If it is dry and worn out, you may need to replace the O-ring before you reassemble your device.
    • Inspect the O-ring inside the carburetor tank. If it is dry and worn out, you may need to replace the O-ring before you reassemble your device.

Conclusion

To reassemble your device, follow these instructions in reverse order.

25 other people completed this guide.

Tim Wirtz

Member since: 01/30/2015

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1 Guide authored

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Cal Poly, Team 6-31, Amido Winter 2015 Member of Cal Poly, Team 6-31, Amido Winter 2015

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12 Comments

I just performed a carb tank cleaning based on your DIY and it took less than 30 minutes! The best part of the cleaning was an immediate start of my mower on the first pull. Thanks

Jerry - Reply

Nice guide. My mower was only running on choke, any other throttle setting and it would die. A quick online search indicated dirty carburetor and subsequently I found your guide. Gave everything a good clean and voila! Good as new.

Tania Miller - Reply

Slide clamp on fuel line back and pull fuel line off carb. plug line with old pen/pencil

Remove two nuts holding carb onto engine. Remove nut holding engine choke arm on top of carb. Then remove two springs and one carb adjust metal arm. Note places of attachment

spray cleaner in all brass jets, use fine wire to clean out all orifices, clean bowl attachment nut. Spray cleaner in to choke area and tip upside down and spray under the bowl needle.

drain old gas out of tank and alternatively add a in line fuel filter as well a new air filter.

clean or repl spark plug

jim steinberg - Reply

Excellent suggestions, as well.

Charlie Farrell -

yes, this is a better guide for cleaning. the other should be called "how to inspect your carb O-ring"

kevin -

My B&S 675 is on a Craftsman WeedTrimmer. It has no Manual choke. Only a primer bulb. I can't get primer bulb to pick up gas. I have put on a new carb and a new bulb. What else could be causing the prob? If I spray B12 in carb it will crank and run. Help please?

Steve - Reply

took off cover, that plastic washer was cracked. what is the part number for that? i need it replaced as this is where a fuel leak was happening.

Scott Dilzer - Reply

Excellent directions, but I have one minor critique. There is a lot of gas that leaks out when doing this. Maybe, suggest pinching the gas line? Otherwise, this was great!

Charlie Farrell - Reply

Have tried everything else before finding this site. Following these instructions will be my last attempt before beating my daughter’s string trimmer to absolute and irredeemable destruction with a sledge hammer. I have a feeling that following these instructions will work and save my daughter a lot of money.

Nona - Reply

I carried out these steps in addition; maybe they should go without saying but worth it all the same.

Before step 1, clean the external area well (I use carb cleaner spray) to remove the crud that builds up in the nooks and crannies and won’t contaminate the carb/air/choke areas.

Before step 3: Clamp the fuel line between the tank and the carb, in case there’s some gas left in the line and the tank. I have done this several times with a partly filled tank and without removing either end of the fuel line; anything to make the job easier.

Before step 5: Stuff some rags or paper towel wad under the tank to catch any residual gas that drips out.

Hugh Jampton - Reply

how to slow rpm on engine

mariecp009 - Reply

I would add that the hex head at the bottom of the bowl is also the main jet…using small wire and carb cleaner to make sure ports are clean. I have three port holes….one that rums all the way thru the sides and one at the bottom of the bolt. I came here to try to verify that the one at the top if it connects to the ones on the side….either it doesn’t, or mine is clogged.

James Mendenhall - Reply

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