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Thread: decompression valve how does it work? does mine work?

  1. #1
    Join Date
    Nov 2012
    Location
    oakley michigan usa
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    61

    decompression valve how does it work? does mine work?

    1983 ytm 200k. It only has pull start and pulls really hard. ive read a little about the decompression valve but dont understand it. And why is there a cable running to the case next to the pull cord? Maybe mine isnt the right model for this? I pulled the vavle up last night and it pulls alot easier but wont start. Any help apreciated thanks! here is what i have:

    and this is the cable coming from the decomp valve to the pull starter area
    1983 yamaha ytm 200k : race cam and cobra exhaust

  2. #2
    Join Date
    Aug 2008
    Location
    MN
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    3,263
    The way its supposed to work is you pull on the starter cord and it pulls the decomp lever on the head so its easier to get it spinning, one revolution and the decomp lever drops back down and it should fire, so holding it up it won't start because then you have no compression.
    ---------------------------------------------------------
    1984 Honda ATC200ES "Big Red"
    1982 ATC200E "Hondie"
    1988 TRX300FW "Project Quad" Still in progress....

  3. #3
    Join Date
    Nov 2012
    Location
    oakley michigan usa
    --
    61
    Quote Originally Posted by kb0nly View Post
    The way its supposed to work is you pull on the starter cord and it pulls the decomp lever on the head so its easier to get it spinning, one revolution and the decomp lever drops back down and it should fire, so holding it up it won't start because then you have no compression.
    thanks alot!!!! i was figuring it should be automatically done because it had the cable. So you think maybe i just need to adjust my cable? i think it had an adjuster on the cable itself.
    1983 yamaha ytm 200k : race cam and cobra exhaust

  4. #4
    Join Date
    Aug 2008
    Location
    MN
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    3,263
    Could just need adjustment, and lubricating the cable. Disconnect the cable from the lever up on the head, if you pull it up with the cable disconnected and let go does it drop back on its own after spinning the motor over? If so then its just the cable or adjustment. On the Honda's that have this it's usually just the cable sticking.
    ---------------------------------------------------------
    1984 Honda ATC200ES "Big Red"
    1982 ATC200E "Hondie"
    1988 TRX300FW "Project Quad" Still in progress....

  5. #5
    Join Date
    Nov 2012
    Location
    oakley michigan usa
    --
    61
    Quote Originally Posted by kb0nly View Post
    Could just need adjustment, and lubricating the cable. Disconnect the cable from the lever up on the head, if you pull it up with the cable disconnected and let go does it drop back on its own after spinning the motor over? If so then its just the cable or adjustment. On the Honda's that have this it's usually just the cable sticking.
    ok thanks. its tore apart right now and no oil in it. ill have to check this after the shift shaft is fixed hopefully soon. But with it hooked up i can pulle the decomp valve up then pull and pull and it wont go back down unless i move it down. ill check the cable.
    1983 yamaha ytm 200k : race cam and cobra exhaust

  6. #6
    Join Date
    Aug 2008
    Location
    MN
    --
    3,263
    Its the cable then i bet, disconnect the cable and see if the spring on the decomp lever makes it drop back down.
    ---------------------------------------------------------
    1984 Honda ATC200ES "Big Red"
    1982 ATC200E "Hondie"
    1988 TRX300FW "Project Quad" Still in progress....

  7. #7
    Join Date
    May 2012
    Location
    ELk Garden WV 26717
    --
    55
    I removed mine fully, But mine starts first pull everytime, so i don't get wore out starting it.

  8. #8
    Join Date
    Nov 2012
    Location
    oakley michigan usa
    --
    61
    Anyone ever have any issues with these decomp valves rattling? Tired of hearing mine. May tear it apart tonight.
    1983 yamaha ytm 200k : race cam and cobra exhaust

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