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piston ring end location problem

in 2 Stroke Technical Questions 13 years ago
Hi first post here.
Also, it is a ROTAX question but not aircraft. I hope that is OK.

I have a type 537 engine, 521 cc liquid cooled. I had a piston failure as a result of a torn carb boot.
The failed piston was wiseco which had the ring ends missing all the intake ports.
The replacement is Kimpex and has the lower ring end is over an intake port (2 ring piston).
I found a used Elko piston, which is suppose to be stock/original. It is like the Kimpex with the ring end over an intake port.
The intake port in question is 180 degrees from the center of the exhaust port.

I am a beginner and have been told the ring ends are never over a port.
Any comments would be appreciated.

  • Re: piston ring end location problem

    by » 13 years ago

    Brian,

    The ring ends are supposed to be 180 degrees opposite the exhaust port. The top and bottom rings are are slightly to the left and right of 180 degrees, but basically 180 degrees from the exhaust side. If I remember correctly, the intake ports are not opposite the exhaust ports but are on each side. Fuel/air is drawn into the crankcase from the carbs and then travels up each side of the cylinder to the intake ports.

    Bill.
      
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  • Re: piston ring end location problem

    by » 13 years ago

    Thanks Bill

    But the lower ring ends go right over the center intake port. Can this be right?

    Brian
    cylintakeview.JPG (You do not have access to download this file.)
      
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  • Re: piston ring end location problem

    by » 13 years ago

    Brian,

    My memory failed me. There is a small port opposite the exhaust as your photo clearly shows. I may be wrong on this, perhaps some of the other guys will jump in and shed some light on it. If i remember correctly, The pins in the piston grooves are not exactly 180 degrees opposite the exhaust port. They are offset so that one is to the right of center and the other is to the left. I think these pins fall just to the left and right of that small center intake port.

    Bill.
      
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  • Re: piston ring end location problem

    by » 13 years ago

    Brian,

    I forgot to add, but I think you definitely don't want the ring ends passing over an intake port. Usually, the spot where the ring ends go up and down in the cylinder leaves a dark vertical line on the cylinder wall and its look like you can see those two lines to each side of the center exhaust port in your photo.

    Bill.
      
    Report

  • Re: piston ring end location problem

    by » 13 years ago

    My goodness you have sharp eyes Bill.

    Yes the Wiseco piston that was destroyed did have ring ends that miss all ports.

    However the new Kimpex piston I have has the ring ends over this port.
    Also an old Elko (made in Austria) piston I have found, which I'm told is OEM, also has the lower ring over this port.

    I just don't know if I should use the Kimpex?
      
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