Small Engines Carburetor Problems and Solutions

Published on March 20th, 2015 | by Jacks

54

Carburetor Problems and Solutions

The following is a chart of potential carburetor problems and possible remedies. This chart is intended to be a helpful guide when troubleshooting your carburetor. Each incident varies in accordance to individual use. Regular inspection of carburetor parts is recommended.

Always consult your owner’s manual for specific Carburetor tuning and recommendations.

Check float shaft for wear and float for leaks or dents

PROBLEM POSSIBLE SOLUTION
  • Engine hunts (at idle or high speed)
  • Carburetor Leaks

Examine idle and main mixture adjustment screws and O-Rings for cracks and damage.

  • Carburetor out of adjustment
  • Engine will not start
  • Engine will not accelerate
  • Engine hunts (at idle or high speed)
  • Engine will not idle
  • Engine lacks power at high speed
  • Engine overspeeds
  • Engine starves for fuel at high speed (leans out)

Adjust main mixture adjustment screw; some models require finger tight adjustment

  • Carburetor out of adjustment
  • Engine will not start
  • Engine will not accelerate
  • Engine hunts (at idle or high speed)
  • Engine will not idle
  • Engine lacks power at high speed
  • Idle sped is excessive

Adjust idle mixture screw

  • Carburetor out of adjustment
  • Engine will not idle
  • Idle speed is excessive

Check for bent choke and throttle plates

  • Engine will not start
  • Engine hunts (at idle or high speed)
  • Engine will not idle
  • Engine overspeeds
  • Idle speed is excessive
  • Engine starves for fuel at high speed (leans out)

Adjust control cable or linage, to assure full choke and carburetor control

  • Carburetor out of adjustment
  • Engine will not start
  • Engine overspeeds

Clean carburetor after removing all non-metallic parts that are serviceable.

  • Carburetor floods
  • Engine starves for fuel at high speed (leans out)

Check inlet needle and seat for condition and proper installation

  • Carburtor leaks
  • Engine overspeeds
  • Idle speed is excessive

Check sealing of welch plugs, caps, plugs and gaskets

  • Carburetor out of adjustment
  • Engine will not idle
  • Engine lacks power at high speed
  • Carburetor leaks
  • Engine overspeeds

Adjust governor linkage

<

  • Engine hunts (at idle or high speed)
  • Engine will not idle
  • Engine lacks power at high speed
  • Carburtor floods
  • Engine starves for fuel at high speed (leans out)

Adjust float settings if float type carburetor

  • Engine hunts (at idle or high speed)
  • Engine will not idle
  • Carburetor floods
  • Engine will not start
  • Engine will not idle
  • Engine lacks power at high speed
  • Carburetor floods
  • Idle speed is excessive

Check diaphragm for cracks or distortion and check nylon check ball for function if available

  • Engine hunts (at idle or high speed)
  • Engine lacks power at high speed
  • Carburetor floods
  • Idle speed is excessive
  • Engine starves for fuel at high speed (leans out)

Check sequence of gaskets and diaphragms for the particular carburetor being repaired


Jack’s Safety Tips: Before servicing or repairing any power equipment, disconnect the spark plug and battery cables.
Remember to wear appropriate safety glasses and gloves to protect against harmful chemicals and debris. View our Disclaimer.

Featured Parts and Products:

Tags: ,


About the Author

Jack's Small Engines has been providing parts for outdoor power equipment online since 1997. We also run a service center for outdoor power equipment like riding mowers, snow blowers, generators, chainsaws, and just about anything else.





54 Responses to Carburetor Problems and Solutions

  1. Alex Fuller says:

    Engine will not start using choke,will start manually choking with your hand what is theinitial carburetor settings

  2. B. Adkins says:

    The engine should start and run at any setting between 1 and 1 1/2 turns out from finger tight. Make sure the needle and seat are both clean before installing the needle, BUT be CAREFUL not to damage either by cleaning with metal (wire). After the engine warms up the idle can be fine tuned for optimal performance.

    Good Luck!

  3. Mark Norman says:

    Just found this site today, wish I had 2 weeks ago. My 12.5 Briggs/Murray mower is old but only
    recently have given me problems. I removed the carb and had it rebuilt for an external leak at the
    intake area, put it on and ran good but with an engine firing miss. Took the plug out and it was dripping with fuel.
    Is this a product of rebuild or is it time for engine work or replacement? Thanks for assistance -Mark N.

    • Daniel says:

      Sounds like the needle is not seating and/or the float needs replacement. Most of the floats in small engines do not have a metal tang to adjust them with unlike snowmobile’s, motorcycles, and outboard boat motors. You will have to take the carb off and dis-assemble it to verify.

      The other thing that could be happening is you are using too cold of a spark plug. To cold of a plug does not ignite all the fuel in the combustion area. If you use too hot of a plug it will overheat and cause detotonation and pre-ignition.

      Just a few things to look at.

  4. Carmine says:

    I have a lawnmower Craftman ( SEARSE) 6.2 horse power front wheel drive . I replaced the spark plug, filter, new carburator , new blade, clean the gas tank and line ,, new (fresh Gasoline ) I get no gasoline into the sparl plug chamber . Can you give me advice on WHY ? I am a retired man and try to safe a dollar . Than you for your understanding , The best Carmine

    • Daniel says:

      Make sure to adjust the pilot screw 1 to 1/2 turns out for initial setting. Verify that the governor linkage is correct. when the engine is off the butterfly should be open. if not that will have to be fixed first.

      Replace the fuel line first. If you use any fuel with ethanol that would be the first thing I would look at. If you are using a fuel filter verify the arrow on it is going to the carb.

  5. Rob says:

    I recently bought a pull behind brush hog. It has a 12.5hp B&S engine on it. I had to change the coil right away due to chipmunk damage. Now that it starts, it runs good, but the choke has to be left on and when I shut it off, it floods. If you try to keep starting it, the plug gets soaked and gas will seep out of the carburetor where the air filter and cylinder connect. There isn’t any gas in the oil. Any ideas?

  6. bob says:

    if I replace carburetor ,idle should be set to run

  7. Bryan says:

    I just replaced the carb on my Kohler engine. When I shut the mower off gas keeps flowing through the carb and runs out. What’s the dang deal?

    • Hi Bryan,

      Likely, you have the same problem as Jide below, I’d recommend checking out the float, pins and valves, be sure they are all properly functioning, if debris has gotten in to your needle valve it may be staying open, or it could be the float malfunctioning.

      Best of luck!

      • Ralph says:

        Unless your float is busted, then it is not your float. Needle seat control the flow of fuel. Also, these units come with an electric fuel cut off located on the bottom of the carburetor. Needs electric charge to activated it, .

  8. Jide says:

    what could be responsible for putting fuel in the carb before an engine starts running

    • Hi Jide,

      The likely cause of this is if your float is malfunctioning. Unfortunately the only way to check this out is to remove the carburetor, clean it, and disassemble it. A problem with the float is also likely to cause flooding when trying to start the engine.

      Check the adjustment on your float pin, and maybe even get a new one, and this should hopefully stop your problem!

  9. Billy says:

    please help, I bought a brand new wood splitter last fall on clearance with a 6.5 Koehler. It sat in my shed until this summer when I pulled it out put it together and put all fluids in and tried to start it. Only premium gas and I pull and pull and pull and it will kinda Pop off and won’t want to go. I’ll choke or no choke or no throttle or 1/2 or full with all positions of the choke and nothing. Took carb off to clean junk out of it. It was perfectly clean, still pulled all jets and screws out cleaned With air gun. Same thing when got it back on. If I dump a little gas down the carb a couple times, I can finally get it to go. After it starts, runs perfect and not a single problem. When it is warm and shut off, it will start right back up. Only cold starts the thing is a pain in the butt. Any input would be great. It’s just frustrating being brand new and thing won’t start when you want it to. Thanks Billy

    • Ron D says:

      I bought a new countryline log splitter with the Koehler 6.5hp. Used it for 12 hours and it started surging/hunting. Finally it stopped running. When I attempt to start it it pops or starts up then quits right away. Is it needle valve issue, sounds like its NOT getting enough gas
      Any thoughts?

  10. Andy says:

    I have a khohler 20 hp vtec engine I t will start when I put fuel in it and shuts off when it burns off. I thought the selnoid was bad, ordered another new and installed , It is getting gas to the carb… but it still does not start. What may be the problem?

  11. Rick says:

    How can you tell on a small diaphragm carb if it is rebuildable or should be replaced. Ts420 won’t start and airbox and carb were full of concrete dust. I don’t want to waste my customers time. Thanks.

  12. dan says:

    hello, have a honda gx160 it will only start with starter fluid then dies. put in fresh gas, cleaned and gaped plug, took carb off and pulled main jet out , cleaned and pushed wire threw openings still n/g. bowl filles up with gas. any thoughts ?

  13. Aubrey Bentley says:

    I have a 20 hp. briggs & straton engine on my riding mower. How can I tell if the fuel solenoid is working right.

    and the wires going to it , do I check only when the key is on to see if it has power to it.

  14. Pingback: How Small Engine Carburetors Work

  15. Mark Z says:

    Installed a new carb on a small 4 wheeler and now when started it goes to full throttle. What do you think is my problem?

  16. John P says:

    I inherited a generator with a B&S twin 18 hp engine (350447) that is 12 years old and never started. I checked the fuel pump (ok), so fuel is getting to carb. I can pour a small amount of gas in carb and it runs fine, but no gas is getting into carb. Any ideas. Thanks

    • Michaela C. says:

      I had same problem. Buy replacement carburetor (no brass nipples) off ebay cheap. Runs marvelous now. Probably from old ethanol fuel sitting in carburetor.

  17. Dallas Jones says:

    I cannot remove the phillips screws to disassemble the carb. any suggestions?

    • Bob Tudor says:

      you are gonna need an impact screwdriver, you hit them with a hammer and they break the screws loose, got mine at harbor Freight for cheap. put anti seize lube on the screws before you put em back

  18. Kurt P. says:

    Hi,
    *Craftsman snowblower would not run full throttle without bogging down.
    *Removed the carburetor, cleaned it (did not touch the float) and put back together.
    *Snow blower started right but was leaking gas out of the carb.
    *Removed carb and replaced all gaskets, now the snow blower will not start and I get NO gas in the carb.

    What could be wrong?

  19. K Gurgel says:

    How do I find BriggsStratton small engine repair manuals on your website?

  20. Austin says:

    I have an older mantis tiller I have no idea what model it is but it’ll only start when I put gas directly into the carb and then only runs for a few seconds. It is getting gas from the tank and if anyone knows how to help that would be great also I already cleaned the diaphragm and I have adjusted to high, low, and idle screws.

  21. Cecily R says:

    OUr snowblower runs but when it engages with snow iit chokes out, the idle is out of sync. the carburetor has been rebuilt, any ideas as to why?
    Thanks

  22. zeeshan says:

    After rebuild my fz16 motorcycle engine, I,m facing a painfull problem, when I start my bike or riding, my rpm gose down for a moment and came back again, its like starving for fuel. But my tank is full. Usually it appears frequently between 2 to 3.5k when I throttle or goes to change the gear. Then again I checked the carburetor by keep the bike in “N” in gear and throttling, I saw, its like my carb is blowing wind, its give a slight sound like “BOOt”when the rpm goes down and vibrates. Its happenig frequently, some times engines also dies. Pls some one help me. I took the bike to several machanics, no 1 giving me the solution, i also changed a orginal new carb but no solution.

  23. Anthony D. says:

    Carburetor is having several problems with associated solutions. If the engine is not accelerated or if the engine drives at high speed, lacks power, then main mixture should get adjusted.

  24. cy says:

    How do you the carburator apart. It looks like the bowl unscrews It is very tight.

  25. milton says:

    I have a craftsman LT1000. Model 917-272420 ser. 032901c006433. Eng. cv492s spec. 27506 kohler pro 18 hp ohv gas is leaking from gas tank to oil. Is the carburetor no good. I have put a carbu. kit on it but still does it.Any help would be good. Thanks

    • sam says:

      i have been trying to get a kohler ch6 going for a friend.
      it has been standing for some 5 years because of a broken starter coil.
      i have cleaned out the carby, and replaced most of the hoses etc.
      my problem is that i can get it to start and run but only if the choke is fully closed.
      Any suggestions would be greatly appreciated.

      sam.

  26. Randy Holloway says:

    I put a bran new carborator pz19 on a gocart an gas is leaking out of the overflow tube an air filter an runs with choke halfway on turn choke off it dies please help

  27. julie says:

    I have a Honda GCV160e lawn mower engine on a Husqvarna flymo. It started last year to leak fuel through the air filter. I cleaned the carb and looked at the float and float pin for wear etc and it all looked good……no leaks in the float. It persistently carried on leaking fuel. Sometimes it would be after twenty minutes and sometimes it would be longer. i have manged to run it for two hours without any problems whatsoever. I bought a new carb and fitted it and it ran beautifully until the next time I came to use it and I couldn’t start it. I took it in and I was told that the float had stuck. It worked but when I refilled with fuel I had trouble starting it but it did eventually start. This season I started my lawn mower on the second pull and it cut beautifully. I stopped it and then moved it round to the front having turned the petrol off in transit. Turned the petrol on and it started. It ran for about five minutes and then fuel came through the air filter again. I asked a garage for advice and I asked if it could be a sticking valve that is causing the problem and they assured me that it was a fuel problem and to clean the fuel tank. I have done this having taken the whole thing off the machine. It did have debris in the tank. And to my surprise dead grass. I cleaned it and let it dry and put it back on the machine. I have just started it having put the old carb on and again because I thought maybe it is the fuel tank, fuel immediately oozed out of the filter. Could a sticking choke cause a problem? Is it still a fuel problem? Is it a sticking valve? I have spent a fortune taking it in and as soon as they get it started they think that it is ok, but it clearly isn’t. It is a 12 year old machine that basically does 2 hours of mowing at the beginning of the season virtually every week and then down to possible every two week come June. I was told by the guy who gave me advice over the phone that he has machines that are over 20 years old and are still running with the same engine and valves.. Is it basically a case of the engine not processing the fuel properly? It doesn’t excuse why I can run it for two hours sometimes. I am really fed up and I know I am a woman and don’t know much about engines but I have had the carb off more times than I care to mention. I am now going to put the new carb back on and see what happens but I am fast losing patience and I am surprised that when I have taken it in they haven’t looked at the possibility of the tank being contaminated. Any help would be appreciated! Thank you so much from a very frustrated lady who is almost frightened to use it! I forgot to mention that the first time it leaked fuel the machine hydro locked and I had to free it. Every time it happens there is fuel in the oil. i was told this was normal as fuel is backing up. i am thinking that it is a valve possibly sticking but again I don’t know enough about engines.

  28. Josh M says:

    My 17hp briggs an stratton on my l100 John deere isn’t getting gas. I’ve replaced hoses, pump an fuel filter. It come thru the fuel filter an after it reaches that it won’t come any further. What can I do . The hoses aren’t pinched or anything is this a vacum problem?

    • Dick Moldenhauer says:

      Josh,
      Make sure you have the hoses correct on the fuel pump. One line is ‘fuel in’ only. Another is ‘fuel out’ only and the third is ‘pressure pulse’ only (from the engine crankcase). It makes a difference. Try slightly pressurizing the fuel tank (put a rag around a drinking straw and seal the fuel tank inlet and blow into the tank-works easiest w/ a full tank) to see if fuel will go farther as well.

  29. elmagnifico says:

    Please sir my tigmax th2900dx is flauntuating that is the sound is not steady i changed the carburator still the same. Please advice me

  30. Paul says:

    I there, i have an old 91 petrol ford courier ute that has developed what i think is a fuel fault in the carb.It is very hard to start but when it does it runs fine, it will idle for a while you can rev it and all seems fine then it will stop and not want to start again. I have checked that its getting fuel to the carb and its got spark, its also done 350k thoughts cheers

  31. Peter says:

    Hi,

    Just bought a used Katana. After my initial ride, the bike has been a pain to start. Replaced the battery and checked my spark plugs, which helped get it started. But today while riding, it shut off once I pulled in my clutch to stop at a stop light. Managed to get it started after playing with the idle and choke, but the bike cut out as soon as I accelerated and switched to 2nd gear. I’ve parked it for now and am hunting the internet for help. So powers that be, any suggestions?

    Thanks

  32. Ned Barkema says:

    New cub cadet ZTR with Kohler 24hp 7000 engine 3.5 hours

    Ran out of gas while mowing. Filled with gas. Unit will not start

    Suspected gas from can was possibly old (2 months)

    drained gas tank from fuel line on the fuel line down line of filter. (filter not plugged)

    Fresh gas.. Spark to both cylinders (in line test light)

    No start … engine cranks but does not fire

    Checked output of fuel pump. Steady stream while engine cranks

    checked solenoid on bottom of carburetor …. the pin retracts as it should when key turns.

    Took the bowl off, full of gas. Ensured the opening that the solenoid valve closes was not plugged.

    Will not start

    putting a tablespoon of gas in the throat of carburetor, engine starts immediately and runs 2-3 seconds until tablespoon of gas is consumed

    Fuel blockage somewhere???? I am at wits end, I’ve never had a problem like this in all my years of small engines. Can take the unit for warranty service but there is a 3 week backlog. May need to buy goats to take care of rapidly growing grass

    Thanks in advance!

    Frustrated

    Ned

  33. david moore says:

    a 97 400 suzki it wont idle what could it be. carb. has ben cleaned haz a pulch fuel pump could that be the problm.

  34. Crystal Davis says:

    My sons Kawasaki ksf 450 ATV, is flooding out when given acceleration. What could it be

  35. Rodney says:

    I have a 17 and a half horse Briggs and Stratton motor Murray lawn mower it turns over good don’t need spark plugs and solenoid I can put some gas in the carburetor in a run that gas out and it won’t run again could the carburetor be stopped up

  36. michael spears says:

    I have an 8hp Briggs motor that is giving me fits. The engine will start and run fine for about 3 min. I have replaced fuel tubing, new carb, cleaned fuel tank, still same problem. I am at a loss. Any help would be appreciated.

  37. rj says:

    Ok so im working with a chipper/shredder and i put gas in the tank and the gas runs staight thru the air filter i took the carb off and sprayed it down i took the bowl off sprayed it out..still running thru the filter not sure wat i need to do to fix it

  38. Thomas John says:

    I’m having yet another carb issue that I could use help with.
    Subject- Honda string trimmer model #HHT-25S.
    I was convinced (by my brother) that a 4-cycle Honda was the ‘way to go’. Fast forward…
    The latest issue……..–having replaced the carb, the gas filter, the plastic ‘purge bulb’ and a new
    air filter it still (so do I) has issue. …
    The purge bulbs does not stay filled with non-ethenol gas. It runs to empty and the engine dies.
    I swear, prime the carb and repeat. It runs for a minute…repeat.
    New purge bulb looks good, and 2 hoses into carb look good. Their clamps are on correctly. The filter at the end of the gas lineinside gas tank is new and looks clean.
    What now?,,,,,,,,,

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to Top ↑