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  1. 1

    Cylinder Bore Size ? Johnson 3hp '52-'54 JW-10

    Have a line on some oversized piston rings (part #203398 superseded to part #378414) for my JW-10. I have decided to go a head and rebuild the power head. According to my parts list, the over sized piston rings are ?.020 O.S.?. I am assuming this means that they are .020 larger than the...
  2. 1

    JW-15 to 1952 - 1954 JW-10 Powerhead Interchange

    Looking at purchasing a rebuilt powerhead from a JW-15 (not sure of the year) and putting it on my 1952 - 1954 JW-10. I'll have to hook the carburetor and ignition systems. Does anyone know if the JW-15 powerhead will fit on JW-10 without any modifications ? In other words, are the JW-10 and...
  3. 1

    Johnson 1952-1954 Jw-10 3hp Piston & Ring Combos

    I would like to increase the power/compression of my JW-10. Currently, the compression is reading about 90 lbs (if my gauge is accurate) in both cylinders. The compression increases to about 145 lbs (if my gauge is accurate) when adding 2 cycle oil to the combustion chambers, testing the...
  4. 1

    1952-1954 Johnson 3HP JW-10 Proper Compression Check

    To clarify the compression testing technique for a vintage 2stroke with pull start. 1.) Unscrew all spark plugs from engine 2.) Ground ignition system: Insert spark plugs back into their boots. Clip alligator lead/wire to the metal at the sparking end of the spark plug. Clip the other end of...
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