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How to tell if I'm on compression stroke

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    How to tell if I'm on compression stroke

    How do I know.if I'm on compression stroke to do a leakdown test?
    Ian

    1982 GS650GLZ
    1982 XS650

    #2
    Maybe remove a spark plug and turn the engine until you feel air coming out?

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      #3
      Originally posted by phydeauxmutt View Post
      Maybe remove a spark plug and turn the engine until you feel air coming out?
      Maybe? Hmmmm
      Ian

      1982 GS650GLZ
      1982 XS650

      Comment


        #4
        How about inserting a wooden dowell in the spark plug hole and watch it while rotating the crank. Or just get a flashlight and look inside
        Roger

        Current rides
        1983 GS 850G
        2003 FJR 1300A
        Gone but not forgotten 1985 Rebel 250, 1991 XT225, 2004 KLR650, 1981 GS850G, 1982 GS1100GL, 2002 DL1000, 2005 KLR650, 2003 KLX400

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          #5
          How about installing the gauge, pressure will build on compression stroke, not on ex. stroke
          1983 GS1100E, 1983 CB1100F, 1991 GSX1100G, 1996 Kaw. ZL600 Eliminator, 1999 Bandit 1200S, 2005 Bandit 1200S, 2000 Kaw. ZRX 1100

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            #6
            If the valve cover is off you can tell by what the inlet cam is doing.
            Down and back up is the tell for the start of a compression stroke.
            97 R1100R
            Previous
            80 GS850G, 79 Z400B, 85 R100RT, 80 Z650D, 76 CB200

            Comment


              #7
              Originally posted by Burque73 View Post
              How about inserting a wooden dowell in the spark plug hole and watch it while rotating the crank. Or just get a flashlight and look inside
              That will get you TDC, but unless you watch the valves, you won't know if it was the compression or exhaust stroke.

              Comment


                #8
                Originally posted by phydeauxmutt View Post
                That will get you TDC, but unless you watch the valves, you won't know if it was the compression or exhaust stroke.
                Put your thumb over the plug hole.
                ---- Dave
                79 GS850N - Might be a trike soon.
                80 GS850T Single HIF38 S.U. SH775, Tow bar, Pantera II. Gnarly workhorse & daily driver.
                79 XS650SE - Pragmatic Ratter - goes better than a manky old twin should.
                92 XJ900F - Fairly Stock, for now.

                Only a dog knows why a motorcyclist sticks his head out of a car window

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                  #9
                  Originally posted by phydeauxmutt View Post
                  That will get you TDC, but unless you watch the valves, you won't know if it was the compression or exhaust stroke.
                  Gotcha....
                  Roger

                  Current rides
                  1983 GS 850G
                  2003 FJR 1300A
                  Gone but not forgotten 1985 Rebel 250, 1991 XT225, 2004 KLR650, 1981 GS850G, 1982 GS1100GL, 2002 DL1000, 2005 KLR650, 2003 KLX400

                  Comment


                    #10
                    Originally posted by Grimly View Post
                    Put your thumb over the plug hole.
                    Since that response was related to using a dowel to visualize the movement, it would be just a wee bit ... difficult to put your thumb over the hole.

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                      #11
                      Great methods given but I'm going to go at this another way. You're doing a cylinder leakdown test, so set the piston at TDC and run your test. If you get leakage rotate the crank 360° and run the test again. The test that leaked less is/was your TDC compression stroke.

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                        #12
                        Or, ... if you simply look through the spark plug hole before screwing in the gauge, you can see the valves to tell whether they are open or not.

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