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Thread: -RESOLVED!- Honda ATC200s suddenly extremely low compression.

  1. #1
    Join Date
    Sep 2022
    Location
    norfolk va
    --
    3

    -RESOLVED!- Honda ATC200s suddenly extremely low compression.

    Thank you so much to all those who chimed in to help a fellow ATC'er in a need of crisis! The bike is back up and running and the kids are loving it! I'm completely embarrassed as to what the fix was am still quite baffled as to why. I stuck a new el cheap'o Amazon special Chinese carb and it fired right up. I have rebuilt/cleaned around 50 of these types carburetors and don't know why this one would not let it even fire up with gas/ether after being completely torn down and cleaned all passages and orifices. Go figure but just relieved were good to go over here, thanks again!


    Hello all and thanks for taking the time to read my post. New member here and am looking for a little advice as this thing has me baffled at moment.

    Trike always ran and shifted great but has been sitting for 2 years and finally decided to get this thing going for my kids. Below steps taken so far as it has me baffled as to the issue(s):

    -Sprayed starter fluid in carb hoping that it would eventually run on its own with the old gas but it never did and had to use a shot of ether each time to start and would run for about 5 secs each time . When it ran with ether it sounded great with nice throttle response and no smoke. You could never hear gas trickling into carb and come to find out the float needle was sticking and not allowing gas to flow into it.

    --Drained out old gas, cleaned fuel filter, cleaned entire carb and jets. Put fresh gas and turned on petcock and this time you could actually now hear the fuel going into the carb fuel bow. I thought yay I fixed it but no. Now it does not even attempt to fire off with the fresh gas and starting fluid!

    ---Checked spark and it is still good so now thinking why is it now not even attempting to start at all?

    ----Checked compression and it literally was at 0 but felt like good compression when hand cranking and blew your thumb out of spark plug hole.

    ----What could have possibly of happened when it was running good on ether just a few moments ago to now no or barely any compression and not even trying to fire over with good spark and gas/ether?

    -----Checked the valve clearances and they are good at .002

    ------Disconnected the decompression cable thinking that somehow the exhaust valve may be sticking and now the compression test shows 20-25 psi but leaks down or looses the pressure fast.

    -------Started thinking that maybe the exhaust valve is somehow coincidentally now sticking or a head gasket just blew out? Not entirely sure if I would buy that as it was just literally running fantastic prior before taking the carb off and cleaning it with a shot of ether.


    Any info, ideas, brainstorming someone can start to throw my way would be most appreciated!
    Last edited by cgcss1; 09-07-2022 at 11:20 AM.

  2. #2
    Join Date
    Apr 2014
    Location
    Edmond, KS
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    2,534
    First off, I'd try another compression tester. Something may be wrong with yours. I haven't seen one where the needle moves back toward zero without you pushing the compression release.

  3. #3
    Join Date
    Jul 2010
    Location
    Arkansas
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    2,207
    Take the exhaust header off at the engine. If it runs, let us know.

    That may sound ridiculous, but if you don't already know why I suggest that and it does run, I'll explain and how it's not that uncommon. It's been a problem discovered several times on this site.
    The story of three wheels and a man...

  4. #4
    Join Date
    Sep 2022
    Location
    norfolk va
    --
    3
    Have already tried that thinking maybe the muffler is clogged, made no difference. Thanks for the suggestion though.

  5. #5
    Join Date
    Sep 2022
    Location
    norfolk va
    --
    3
    Damn if you weren't right! I used another compression tester and it now shows 135 psi and is not leaking down. Still not firing off with ether or gas and spark.

  6. #6
    Join Date
    Apr 2014
    Location
    Edmond, KS
    --
    2,534
    At least the compression mystery has been solved. Now on to the not firing. It sounds crazy, but did you try a new spark plug? Sometimes they can have good spark while in the open, but not have good or maybe any spark under cylinder compression. Even if it doesn't make a difference, it's only a few dollars.

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