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  1. #1
    Member
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    Aug 2012
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    Monroe, Louisiana
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    74

    Yamaha fouling one plug.

    I have a 2000 OX66 Yamaha225. It fouls one plug. Changed the plugs, and it one outing fouled one plug. If this happened to you, what was done to fix it. I would like to know what you did to fix it and not what I need to check so I can hit those parts first. I just cleaned VST tank, put in 3 lp pumps. Will clean o2 sensor next. I’m not sure what the plug numbers would be, but if you are looking at the back of the motor, it is the one in the middle on the right side that is fouling. Thanks.

  2. Member
    Join Date
    Jun 2006
    Location
    ROSEVILLE
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    47
    #2
    Following... had same prob for almost 2 years now... GOOD LUCK ~

  3. Member
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    Feb 2018
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    3,153
    #3
    What brand of oil are you using?

  4. Member
    Join Date
    Aug 2012
    Location
    Monroe, Louisiana
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    74
    #4
    Yamalube.

  5. Member
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    Jan 2013
    Location
    Winterville, GA
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    1,261
    #5
    I had that issue 2 years ago. I changed from Yamalube to Penzoil and then I went with a different plug, I think an R8 as opposed to the R9. No more issues, motor runs great.

  6. Member
    Join Date
    Sep 2014
    Location
    Dallas, TX
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    1,104
    #6
    Have you had your injectors cleaned, flow tested, and adjusted? When I had mine done, 3 of the 6 were running rich.

  7. Member berudd's Avatar
    Join Date
    Apr 2013
    Location
    Morrisville, NC
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    7,071
    #7
    Are you sure that cylinder is firing well? I lost a coil on my Optimax and the plug looked fowled. Don't know how this would apply to a Yamaha though.
    Bruce
    2019 20 TRX Patriot
    Mercury 250 ProXS Fourstroke
    HDS 12 Live - Console
    HDS 9 Live - Bow



  8. Member
    Join Date
    Aug 2012
    Location
    Monroe, Louisiana
    Posts
    74
    #8
    I have a coil ordered. I have read a few threads elsewhere that say the thermostat may be stuck and keeps it in warm-up mode and will foul plugs. Will check those today. Ordered them anyway. Have not changed those in 3 years.

  9. Member
    Join Date
    Aug 2012
    Location
    Monroe, Louisiana
    Posts
    74
    #9
    Ended up blowing that piston. Headed to the shop. My mechanic told me it is probably from a vibration from a bent prop shaft or bent prop. He says the ox66 has a pin that will eventually vibrate out of a piston if you have a bad vibration. I did have a bent shaft years ago and my prop has two bent blades now. Only noticed it at idle speeds but didn’t think nothing of it. He says this will cause you to burn a single plug if that pin comes out and eventually blow if not repaired. He will know for sure when he begins rebuilding Tuesday. Since I’m not much of a mechanic with the right terminology, I will find more on this pin he’s talking about. He says when he pulls the piston, the pin will fall out. I will let you know when I find out for sure what caused the piston to blow.

  10. Member
    Join Date
    Mar 2017
    Location
    Georgetown, TX
    Posts
    767
    #10
    It's called a locator pin to keep the rings stationary on a 2stroke. Common failure. You'll understand after reading this article from Wiseco.

    http://blog.wiseco.com/2-stroke-locating-pin
    Lake&Bay Boca
    SHO

  11. Member
    Join Date
    Jul 2014
    Location
    Chesterfield VA
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    3,402
    #11
    Any concerns with de-carboning an engine with regard to the locator pins? Any risk of loosening them up by de-carboning? Or the opposite, can carbon buildup lead to them coming loose?
    Kevin | 2000 Champion 19​1 | 2000 Yamaha OX66 200hp

  12. Member
    Join Date
    Jul 2014
    Location
    KALKASKA MICHIGAN
    Posts
    4,065
    #12
    IMHO no, carbon will cause a hot spot and detonation. The detonation will rattle a pin out. Never heard of vibration causing them to come out? Decarb is always a good thing if done right. CJ
    2002 X19 200HP OX66 HO Vmax,HPDI lower, it lives, thanks Hydro Tec.