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General Product Question

    Bob Johnson
    I have a 123L Husqvarna String Trimmer that wont start. I...
    General Product Question posted May 21, 2018 by Bob Johnson, last edited May 21, 2018 
    66 Views, 2 Comments
    Question:
    I have a 123L Husqvarna String Trimmer that wont start. I have installed a NEW fuel primer pump bulb, a NEW flywheel, a New ignition module, NEW Champion #RCJ7Y spark plug put in FRESH fuel, and cleaned the air filter...I checked the compression and it has 50 lbs of compression...I also checked the "on/off" switch and it is working properly

    It IS getting spark to the plug....I have even "primed" the engine by putting gas directly into the spark plug hole and have even tried spraying STARTING FLUID straight into the plug hole.....Still WON'T EVEN fire briefly.....

    So, if I'm getting spark, fuel and air (and 50 lbs of compression) why won't it AT LEAST fire?

    The only thing I can think of is TIMING but I installed the flywheel correctly.....PLEASE HELP ASAP!!!

    Can I speak to an engineer?

    ALSO....What is the compression SUPPOSE to be for my trimmer?....Is 50 lbs sufficient?

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    Answer

     

    • Eugene Rounds

      Well I just master mechanic and not a full blown engineer but I should be able to help.

      First the compression is way too low as most 2 cycles require at very minimum of 100 psi to start and most trimmer when new usually have between 120 to 145 psi compression. Now if it was a 4 cycle engine you could get with 65-70 psi compression.

      Now for the bad news as you just probably wasted your money trying to repair an unit that has a bad PNC (piston and cylinder). But your complete write off pull the muffler and check the cylinder condition through the exhaust port. If no scoring it might be simply a stuck ring. Scoring of cylinder cause complete lost at the top the compression but a compression gauge will only read average compression. I got a Stihl 029 chainsaw that has 145 psi but has upper cylinder damage and it will not even hit due the lost compression at the top of the stroke.

      Best of luck and hoping it is just a stuck ring.

       

       

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      • Bob Johnson

        WOW! Thanks for the reply Eugene!.....I had looked everywhere on the web to find out what the compression SHOULD be but I could not find it anywhere.....Since it was producing 50 psi consistently I "ASSUMED" that 50 psi must be sufficient....I had no idea that the psi should be anywhere near what you say.

        I removed the muffler and inspected the side of the piston and the ring.....There didn't appear to be any scoring on the piston but THE RING APPEARS TO BE STUCK  just as you suspected!...….I picked at it with a small screwdriver without success and so I have prepared a mixture of 50/50 kerosene and Gumout injector cleaner......I filled the cylinder with the mix and will give it a day or two to see if the ring becomes free in the groove of the piston.....As you said, I invested a bunch of money into fixing it so far and so I'm crossing my fingers that I can get the ring to move freely and the compression is restored....I'll let you know what happens.  Any other suggestions?

        Again, THANK YOU SO MUCH for your response, Eugene

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