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  1. #1
    Member NJfishinGuy's Avatar
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    Ox66 250 compression numbers

    Trying to find out what a stock 04 ox66 250 should have compression vs one with cut heads? Mine is 120-123 across all 6. Was told by someone that it's a bit higher then normal for a stock motor. Thinks the heads may have been cut. I'm new to Yamaha so I'm not sure. Any insight?

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    #2
    The 250 has tighter heads and yours sounds about right. Mine is 127-130 with HT's rec heads. Cj
    2002 X19 200HP OX66 HO Vmax,HPDI lower, it lives, thanks Hydro Tec.

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    #3
    CJ, what octane do you run? Any fuel additives?

  4. Member HaulinBass's Avatar
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    #4
    Should be at least 89 with rec heads.
    Larry Eby, 2004 ChampioN 188 Elite/2003 200 Hp Vmax OX66
    "Romans 10:9"

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    #5
    90 min ethanol free, sea foam with every tank. Ring free every 2-3 or so. I'll dump 5 gallons of 110 in with a full tank for winter storage. Cj
    2002 X19 200HP OX66 HO Vmax,HPDI lower, it lives, thanks Hydro Tec.

  6. Member HaulinBass's Avatar
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    #6
    Stabil, seafoam and ring free mixture with every fuel nozzle. HT said at least 89 but more is better as you wrote.
    Larry Eby, 2004 ChampioN 188 Elite/2003 200 Hp Vmax OX66
    "Romans 10:9"

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    #7
    I have the rec heads, Carson reeds, and lightened flywheel on a 2005 300 HPDI. I use Pennzoil XLF, and treat the fuel with a quart (16 oz.. Marvel MO & 16 oz Lucas Fuel Treatment). Decarb once a season with Blaster Small Engine Tune-up. Everyone has there preferred fuel cocktail. I use 90 ethanol free here in MD

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    #8
    CJ - what are you calling "rec heads?"
    Lake&Bay Boca
    SHO

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    #9
    Quote Originally Posted by ClarkBird View Post
    CJ - what are you calling "rec heads?"
    Hydro tec's recreational heads. I believe that is what they used to be called, heck I cant even find "heads" on their web site anymore. Just phase kits now. 1 st bump over stock heads for compression. I would have went higher but still need to be able to buy fuel in Canada without having to worry about detonation. CJ
    2002 X19 200HP OX66 HO Vmax,HPDI lower, it lives, thanks Hydro Tec.

  10. Iowa/Wisconsin/Hunting & Gun Lodge/Stroker Moderator Wags's Avatar
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    #10
    They still have heads listed on their site.
    LeaLea

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    #11
    Where do you get 110 CJ? What is your Seafoam dosage? Thanks

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    #12
    Local station has Sunoco standard and that is a non oxygenated fuel at 110. I either keep that around or the supreme at 112 for the dirt bike and sleds to add to pump fuel. For the sea foam I will use 12oz or a little more per 25 gallon tank. If I start seeing carbon I will do a decarb with a separate tank and a 25/75 mix but so far it is running very clean inside. CJ
    2002 X19 200HP OX66 HO Vmax,HPDI lower, it lives, thanks Hydro Tec.