Cylinder dowel
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Thread: Cylinder dowel

  1. #1
    Member jamesblown97's Avatar
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    Cylinder dowel

    So i took everything apart for a top end and realized theres only 1 cylinder dowel. How important is it to have all 4.

  2. #2
    Senior Member 2ndmoto's Avatar
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    Needs 2 to be fully constrained
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  3. #3
    Senior Member american opel's Avatar
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    yep only 2 but is a must have
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  5. #4
    Super Moderator Big_Mike's Avatar
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    I always thought the dowels were mainly for alignment. Aren’t the cylinder bolts doing the constraining?
    1986 Honda FourTrax 250R
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  6. #5
    Senior Member 2ndmoto's Avatar
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    You are saying the same thing. By alignment, the cylinder is not free to move in X, or Rz, thus constrained in these directions.

  7. #6
    Super Moderator Big_Mike's Avatar
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    If the dowels were not there, would the base cylinder bolts not line up?
    1986 Honda FourTrax 250R
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  8. #7
    Senior Member 2ndmoto's Avatar
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    The bolts would line up. Typically a through hole will have 200-1000 micron of clearance. It's this excessive tolerance that the dowel takes up. This keeps the sleeve nice and tighty with the rod and piston.
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  9. #8
    Super Moderator Big_Mike's Avatar
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    I just learned something new!!!!
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  10. #9
    Senior Member acecarlos's Avatar
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    Quote Originally Posted by Big_Mike View Post
    If the dowels were not there, would the base cylinder bolts not line up?
    If you mean cylinder bore to crankshaft center-line....Only if you got lucky during assembly...:-)

    Quote Originally Posted by Big_Mike View Post
    I always thought the dowels were mainly for alignment. Aren’t the cylinder bolts doing the constraining?
    The dowels are for alignment as well as constraining, much more an alignment function, however; they do constrain as well.

    Quote Originally Posted by jamesblown97 View Post
    So i took everything apart for a top end and realized theres only 1 cylinder dowel. How important is it to have all 4.
    Well one only is not that bad, you do need both dowels for full alignment & constraint, however; having only one in place prevents the cylinder from moving front to back, it still allows an 'arc' movement from right to left or vise versa. Most likely, since the piston has more than 2MM right to left play built in by the piston to wrist pin/upper rod clearance, the performance loss was not noticeable...wear and reliability would be a bigger concern.

    Best to always run both dowels in place as designed.

    Carlos


 

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