What to check when your small engine surges



This is a “video response” to MiWilderness’ (https://www.youtube.com/user/MiWilderness) question about a surging lawnmower engine. Surging of engines means the engine is either getting too much air, or not enough air. These are some simple and cost-effective things you can try at home.

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45 thoughts on “What to check when your small engine surges

  1. alot of times it isnt the air filter its because the engine isnt adjusted right or the carb needs to be cleaned, also if you get dirt in there when u take the filter off, it wont do anything to the carb but you will probably looking at an engine rebuild sometime up the road good job on the video tho

  2. i wouldnt try to turn it down to 1 and a half turns i would turn it counter clockwise till it stops surging because usually it is because it is not getting enough fuel.

  3. Good instruction. Anyone should be clean or change their mower's air filter after watching your video. Thanks

  4. I would clean the air filter a little bit further away from an open carburetor. But, very good instructions that are easy to understand.

  5. often there is dirt caught on the carb pick up screen since these news emissions requirements call for such a lean mixture, a small obstruction can lead to big issues. my video response is how to remove your typical carb. I hope it helps.

    oftentimes this will be the problem instead of the filter on modern mowers. . .

  6. I have a basic knowledge of gasoline engines, 4 and 2 cycle.Your videos help me a great deal.You are thorough ,easy to understand and a GREAT help to many people.Thankyou so much for what you are doing.

  7. First check the gastank and fill it, then check the sparkplug and be sure that the contactdistanse is 0,5 mm. Then check if the oil have floaten into the cylinder. Then check the fuelleader and then check the airfilter. It is not always the airfilter 😉

  8. Thanks for this Video.
    I have cleaned the Air Filter & Changed the Spark Plug on mine, already, but the revs are still going up and down – the only exception being, when there is a 'Load' on the blade – so (after watching your video) I'm going to go out tomorrow and adjust the Air Mixture & hopefully fix it once and for all.
    PLEASE keep making these videos as they help and inspire many people – Not All of whom, will leave a comment.
    Many Thanks, again.

  9. your float valve will often randomly stick (due to the fast degrading ethanol gas now) which will cause a surging to happen out of the the blue always be sure to clean the carb and make sure ur float bowl valve is opening and closing properly and easily otherwise the surging will happen because the motor is using up the gas in the bowl quicker then it can be refilled

  10. Your video was good. I would just like to add, after cleaning the air filter. Make sure it is dry. I have let it dry in the sun a few hours. After it has been cleaned and dried, take some engine oil and apply it to the filter. I soak it down then squeeze it out leaving a thin film. Then it is ready to put back together.

  11. Hello,
    I've had this surging problems on this type engine which sometimes it could be the intake tube,If you remove the starter housing this tube goes from the carb. to the cylinder head (intake) Sometimes it can be the screws at the cylinder(check gasket also),Also Ive seen this tube being cracked from loose carburetor screws.
    Mr.B.

  12. It's never the air filter that causes the problem.  Just throwing a new filter in it isn't going to fix it. It's probably cause the air filter is clogged and it let dirt past it and now the carb is dirty, which is the real reason for the surging.

  13. U have a mouse nest under the fan and cooling fins my friend u need to take off starter cover and washout with water and air then adjust mixture's and tighten down carbscrewed down on the gastank clean out tank may have water and pickup tube bottom on carb may be dirty

  14. Best thing to narrow it down is to take a blower to it and check for leaks and see if it's sucking air where it shouldn't be. Or if you think it's a clogged air filter then just take it right off and test it. My guess would be dirty carb or governor tho.

  15. In my opinion, run the engine without the air filter. If it runs fine then, you found the problem. If it still surge, its an indication that your carburetor could be dirty. The setting of the air/fuel mixture doesn't change out of the blue. If you have to "add" more air to the setting, its a sign that the engine runs too rich therefore, the air intake could be compromised by minute particles (fine powdery sediments) inside the carburetor.

  16. Surging or "hunting" (the true technical term) is usually caused by a lean carburetor fuel/air mixture. To easily check if that's the problem, run the engine with the air filter/housing off. Slowly close the choke or slowly cover the carb intake. If it smooths out, you're running too lean. The only other thing that'll cause hunting is something (a twig) touching the governor rod and/or spring/lever(s) which is unlikely. Modern lawn and garden equipment is already set lean from the factories to pass emissions. Whatever you do, don't listen to that donyboy73 half-wit. He couldn't pour piss out of his boot if the instructions were on the heel.

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