How to Diagnose Two-Cycle/Two-Stroke Engines

Mark is here to walk you through the steps needed when diagnosing your two-cycle engine issues. These steps will be the same for all the two-cycle tools in your lawn equipment fleet.

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35 thoughts on “How to Diagnose Two-Cycle/Two-Stroke Engines

  1. I have a ryobi hedge trimmer ht26 and I put carb clean in the card and still did not start it had spark and the compression was good at 105 I also check the spark arrester and it was good could you help me

  2. Hi therethank you for the video. Could you please advise me on how to make my old Walbro non thumb pump carb have the ability to have a fuel pumping or primer capability

  3. Hi Mark, the problem with my trimmer is that doesn't start when it get hot, or if it was running for about 10 to 20 minutes. It is easy starting when it is cold. Why is it?

  4. Thanks! My Shindaiwa trimmer runs for about 10 minutes…Then, It will idle but won't take throttle… Would that be the Ignition coil?

  5. although it's better to have a spark tester, it's good to just hold the spark plug against the engine casing and look for a spark at the gap. I. couldn't find my spark tester and just did this instead of wasting my time. Don't use your bare hands to hold spark plug against engine casing.

  6. I have also found the exhaust or muffler gets clogged up alot. I have noticed that gas caps hold a about a half a bar of pressure then release when pressure gets higher than that. If I am running without the gas cap will that cause a fuel and air mixture issue running rich maybe or even worse lean? Thanks Mark and you have saved me several trips to the shop. I think I have similar smaller chainsaw called a 45. What testing equipment would you be that you say I probably don't have to test the plug and strength of the spark being made. I try to see if it will cross a 8mm gap consistently. I have used a little fine sandpaper on the protruding metal parts on the coil. Why is 120 to much compression. I have several items that say they should in perfect operating condition have atleast 150lbs and up to 185. A friend had one that was around 210. I have a weedeater that is a mess that hits sometimes up to 280 lbs. Why is that one not releasing the pressure? Its been cleaned out well and is a basic two so valveless.

  7. What could be the case if my engine doesnt start. It gives a pop or few when i pull the rope, but doesnt fully start up. I changed the spark plug and cleaned the carb (before that the engine was fully dead).

  8. the compression amounts quoted the technician . are way off . ive seen very few 2 cycle units that WOULD run with less than 90 psi comp . and also seen compression readings as hi as 150 psi . it depends on the manufacturer of the equipment as to weather it has 1 pr 2 rings or not . basically cheep vs expensive

  9. great video's i have a problem can you help with advice please fs stihl 120 strimmer no spark new plug , new coil ,regapped the coil at differn't settings checked the switch its fine tried with kill switch off no joy magnets are fine the only other thing i can think of is that the keyway has gone on the flywheel ! what's your assumption please , thanks .

  10. Hi

    I have a chainsaw that is hard to start when it gets warm or you let it sit idle for 5 mins any ideas? I have cleaned the exhaust and spark arrestor screen, thanks Ian

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