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Oversize piston size: How to choose?

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  • Oversize piston size: How to choose?

    Hi, I have a '98 STX 1100 that I ran at WOT with the cooling hose disconnected ['**** thing popped off, my fault] , and I cooked the engine. A couple of months ago, I obtained the gaskets and seals from SBT, and last night, I began fixing the engine in earnest. After I unbolted the cylinder block and split the cases, I realized one ring had seized in a piston. Another piston looks a little scuffed at the top. I want to replace all three of them.

    The front cylinder already has a sleeve, which was sized for a new stock-size OEM piston and rings. The other two cylinders are the original Nikasil cast-in sleeves, and have been lightly polished when I last rebuilt the engine, to help seat the new rings I had put on the stock pistons. The engine had about 120 hours it if I recall. All three sleeves look all right to me, with maybe a slight cross-hatching required again to seat the new rings I will put with the three new pistons.

    I've actually thought about replacing the whole engine with an SBt rebuilt unit, but when adding the shipping to and from Haiti, I just can't justify doing that. So I'd like your opinion on a couple of questions:

    1) For the size of the pistons, should I take the 1st oversize [.5 mm]? Or is it better to go straight to the 2nd oversize [1.0 mm], based on the description I've given above of the cylinder block and sleeves? My biggest concern is making sure I get the right size pistons. I have found a qualified machine shop to bore the sleeves.

    2) Along the same lines, can the original Nikasil sleeves be bored, or must I replace them with aftermarket sleeves, like I did for the first cylinder?

    3) How much will it be for shipping to Florida [regular shipping] 3 piston and ring sets? What about for a top-end kit?

    4) Please include any other pertinent information you can think of. I'm sure it will be useful. Any other readers who have gone through a similar rebuild themselves, thanks for sharing your experiences, and giving your advice.

    Kind Regards, :D

    Gigi
    No more Jet-Ski's for this boy...

  • #2
    I think I can help with question 1 and 4. I found the following info on another site.

    Our testing did cast some doubt on the "bigger is ALWAYS better" mentality that most folks apply to displacement. The stock Kawasaki 1100 cylinder castings can accommodate over boring up to 83mm (1151cc) without resleeving. Increasing the stock 80mm (1071cc) bores to 81mm (1097cc), makes for a very big increase in overall power that is well worth the cost. Further increasing the bore diameters to 82mm (1125cc) makes for an increase that is only slightly better than the 81mm. Overboring to 83mm (1151cc) makes for no increase at all over the 82mm.

    As to question 4. Through my experience with Oval Track V-8's it is known that when you get your cylinder too thin you have heating and cylinder cracking problems. We would often cure it with extra oil coolers big radiators and a longer connecting rod that would put less load on the cylinder walls half way up and down on a stroke. 2 Strokes are new to me. Most of the cylinder is missing on both sides and their is plenty of water for cooling. And the carbs are goofy.

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    • #3
      you should re-sleeve the cylinders. Please contact sales for shipping information.
      SBT Tech Support is here to help with your problems.
      We try to answer each question quickly and accurately.
      Please do not use Private Messaging for Tech Support, use the forums.

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