Good Compression Tester

Discussion in 'Tech Area' started by Korbon_Dallas, Oct 13, 2020.

  1. Korbon_Dallas

    Korbon_Dallas Member

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    Can someone supply a link to buy a good 'inexpensive' Compression tester for my '70 CT? I was looking at them all over the Internet and I was going by the size socket I use to remove the Spark Plug? Is this the correct way to find the right size as I couldn't find any that were that size? The socket I use is 5/8th inch. Thank You in advance.
     
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  3. Gary

    Gary Well-Known Member

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    What your looking for is any tester that has a 10mm adapter, 12mm is for larger Hondas, 14mm for modern cars 18mm older cars. Usually they all come in one set
     
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  4. Korbon_Dallas

    Korbon_Dallas Member

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    Ok. Thanks for the helpful info.
     
  5. Korbon_Dallas

    Korbon_Dallas Member

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    Is size M10 the same as 10mm?
     
  6. racerx

    racerx Administrator
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    Yes, that's just the standard nomenclature..."M10" = 10mm. With bolts & studs it'd be "M10 x whatever the overall length is", in mm.

    Heads-up, most compression testers tend to read lower than actual combustion chamber PSI on small (72cc & lower) displacement engines, due to hose volume. A good way to adapt is starting with a fresh top end that has full compression; whatever reading the gauge gives you should be reasonably (i.e. usable for practical purposes) reliable as a "full compression" reading that can be used to track any compression loss over the years/miles. With 12" flex hose, my Craftsman compression gauge typically shows around 125psi on a freshly build 49cc motor, 145-ish on a CT70. Your results may vary, depending upon hose and internal gauge volume.
     
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  7. Korbon_Dallas

    Korbon_Dallas Member

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    Compression is 145, so why do you think it doesn't seem to have the power after it starts to wind out, like about 2/3's throttle?
     

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