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  1. #1

    Cool opinions wanted from engine builders

    Yamaha 760 85mm (max bore) rear cylinder slightly scored from air leak/lean condition, I have the entire motor apart down to bare cases..machine shop guy looked at it and says just hone it "anything left on cylinders won't amount to a hill of beans". Three options : #1) I was thinking of going with 85mm wiseco pistons or pro-x... hone both and put it together.#2) I would try to buy some used cylinders at 84mm and bore them.#3) buy some new sleeves and I have a friend who can put them in.(but hear that oem sleeves are the hardest/long lasting) I plan to use all new oem gaskets/crank seals. Thanks for your opinions.
    Last edited by Jump On It; 02-10-2008 at 04:16 PM.


  2. #2
    ....back from the dead.... J-ME's Avatar
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    85.50 is OEM max bore. Wiseco makes 86MM pistons.

    does that change things?

  3. #3
    group k,sbt and riva racing say 85.00mm is max on 760 oem sleeves. What is your source on this ? Riva sales book says 85.50/86 require re-sleeving ?

  4. #4

  5. #5

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    Can you catch your fingernail in the score? If not you should be ok.. kinda hard to say without seeing it. I have had many cylinders come in from sleds - cold seized and scored up. Guys didnt always have the money to bore/sleeve - compression would be fine with a good hone.

    The right way is always to bore it or sleeve it if its at max bore.

  6. #6
    Can anyone verify max bore on a yamaha oem 760 ? 85.0mm ? see above

  7. #7
    cheatin' piston popper addicted's Avatar
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    I have also heard that 85.5 is safe, 86 is absolute max.

  8. #8
    ....back from the dead.... J-ME's Avatar
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    I stand corrected.

    My understanding was that they are they same sleeves at the 1200npv.

    After doing some looking around it looks as though 85mm is it.

    Sorry for the mis-info.

    Try going with a forged piston, as you will have to open the bore up some to get the extra clearance. (compared to cast) This may get rid of the bore imperfections you are talking about.

  9. #9
    Try going with a forged piston, as you will have to open the bore up some to get the extra clearance. (compared to cast) This may get rid of the bore imperfections you are talking about.[/quote]

    That is what I have been thinking about it may do the trick.One Fl guy today told me he is running 86mm pro-x in his oem 760 cyl and it works great !

  10. #10
    Tool Bag water worx's Avatar
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    If they make a piston ...run it.

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