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  1. #1

    Found comp proublem

    Ok i starting building my motor today and found the pistion i have been running in it are size b and i need size c to have .004 between the pistion and bore so this would explain why i only had 115 psi on each pot with a shaved head.
    Now it should realy get up and go already with the riva ingntion mod and on side bills carbs done, new reeds with fresh motor should be great can not wait.

  2. #2
    Trying to find how much psi i put into the motor when i preasure test it and i have made my on setup but im going to put it in a tub of water like WFO did first up then i can get a better look at the hole motor
    Is there any down side to that?

  3. #3

    Join Date
    Jun 2008
    St Clair Shores, MI
    You want .004 (4 thousandths of an inch) between the bore and the cylinder. Any tighter and you'll sieze it up.

    If you're running forged pistons it should be more.

    Across all 3 piston sizes there is only .0008" difference.

    If the cylinders are dry when you do a compression check you'll get low readings. Try pouring a small amount of oil in each cylinder - just enough to wet the rings.

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