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    No compression?

    OK, so no more clicking, the timing is set by the manual, it spins freely, all put together. Go to start it and... the starter spins, sounds more high pitch than usual. I assume because there is nothing resisting it, so no compression?
    All the bolts are fitted tight, the crankshaft and camshafts spin... but doesn't start. I did not replace the head gasket (I know, I know, I should. I wanted to see if I could get by with the same one. I should hopefully get money tomorrow, so I can go buy one).

    Here's a video for reference: https://vimeo.com/521670017
    Last edited by ZombiePotatoSalad; 03-09-2021, 10:00 PM.
    1980 GS550E

    #2
    You can take the plugs out and feel with your finger if its moving air if you don't have a compression tester. Other than that, check for fuel/air and spark.
    ---------------------------------------------------------------------------------------------------
    Bikes:
    2016 Suzuki TU250X (Daily/Commuter)
    1982 Suzuki GS750T (Project)
    1979 Suzuki GS750 (in pieces)

    Cage:
    2005 Subaru WRX Wagon sh*t box

    Comment


      #3
      Originally posted by Jimmbuzz View Post
      You can take the plugs out and feel with your finger if its moving air if you don't have a compression tester. Other than that, check for fuel/air and spark.
      I don't have a deep socket to undo the spark plugs. I have to go buy one.
      1980 GS550E

      Comment


        #4
        Not sure why you would attempt to start the bike without the valve cover on. Also not clear how you would check compression but with a compression gauge in the spark plug hole. Spark plugs that you haven’t taken out of the holes.
        Rich
        1982 GS 750TZ
        2015 Triumph Tiger 1200

        BikeCliff's / Charging System Sorted / Posting Pics
        Destroy-Rebuild 750T/ Destroy-Rebuild part deux

        Comment


          #5
          Originally posted by Rich82GS750TZ View Post
          Not sure why you would attempt to start the bike without the valve cover on. Also not clear how you would check compression but with a compression gauge in the spark plug hole. Spark plugs that you haven’t taken out of the holes.
          It wasn't catching, so it wouldn't start. I had to see if the camshafts were turning while the starter was engaged. It sounded higher-pitch than normal, so at I thought something wasn't turning properly.
          1980 GS550E

          Comment


            #6
            the cams may be 180 degrees out of phase so no compression. It's easy to do.
            Ed

            To measure is to know.

            Mikuni O-ring Kits For Sale...https://www.thegsresources.com/_foru...ts#post1703182

            Top Newbie Mistakes thread...http://www.thegsresources.com/_forum...d.php?t=171846

            Carb rebuild tutorial...https://gsarchive.bwringer.com/mtsac...d_Tutorial.pdf

            KZ750E Rebuild Thread...http://www.thegsresources.com/_forum...0-Resurrection

            Comment


              #7
              Originally posted by Nessism View Post
              the cams may be 180 degrees out of phase so no compression. It's easy to do.
              Is it that simple? Could you elaborate? I can go get a picture of the camshafts.
              I followed the guide set in the manual: Advancer set to T, 1 on the exhaust cam flush with the area where the cylinder head and head cover meet, 2 pointing upward. 20 pins over to the intake cam, where 3 is pointing. I'd upload pictures, but it keeps saying upload failed for some reason. I try an image link, that fails too.
              Last edited by ZombiePotatoSalad; 03-09-2021, 11:56 PM.
              1980 GS550E

              Comment


                #8
                Doesn't sound too strange.

                Originally posted by ZombiePotatoSalad View Post
                I don't have a deep socket to undo the spark plugs. I have to go buy one.
                Do this, otherwise you can stop wrenching on your bike (You'll need one anyway to maintain your bike).

                As usual, one needs air (and compression for ICE), spark and fuel to get combustion An old trick is to drop a teaspoon of fuel down the spark plug holes, this gets most engines to fire (for a few revolutions).
                If not, you'll know that either there's an issue with the ignition or compression (or both), and can go from there. If it does, you can begin troubleshooting the carbs.
                Last edited by roeme; 03-10-2021, 08:32 AM.
                #1: 1979 GS 550 EC "Red" – Very first Bike / Overhaul thread        New here? ☛ Read the Top 10 Newbie mistakes thread
                #2: 1978 GS 550 EC "Blue" – Can't make it a donor / "Rebuild" thread     Manuals (and much more): See Cliff's homepage here
                #3: 2014 Moto Guzzi V7 II Racer – One needs a runner while wrenching
                #4: 1980 Moto Guzzi V65C – Something to chill

                Comment


                  #9
                  Originally posted by roeme View Post
                  Doesn't sound too strange.



                  Do this, otherwise you can stop wrenching on your bike (You'll need one anyway to maintain your bike).

                  As usual, one needs air (and compression for ICE), spark and fuel to get combustion An old trick is to drop a teaspoon of fuel down the spark plug holes, this gets most engines to fire (for a few revolutions).
                  If not, you'll know that either there's an issue with the ignition or compression (or both), and can go from there. If it does, you can begin troubleshooting the carbs.
                  I originally had one, but lost it when we moved.
                  1980 GS550E

                  Comment


                    #10
                    Originally posted by ZombiePotatoSalad View Post
                    Is it that simple? Could you elaborate? I can go get a picture of the camshafts.
                    I followed the guide set in the manual: Advancer set to T, 1 on the exhaust cam flush with the area where the cylinder head and head cover meet, 2 pointing upward. 20 pins over to the intake cam, where 3 is pointing. I'd upload pictures, but it keeps saying upload failed for some reason. I try an image link, that fails too.
                    When you set up the cams as described, did the notches on the right hand side of the cams point inwards towards each other (correct) or outwards away from each other (not correct)?
                    1981 GS850G "Blue Magic" (Bike Of The Month April 2009)

                    1981 GS1000G "Leo" (Bike Of The Month August 2023)

                    Comment


                      #11
                      Originally posted by 2BRacing View Post
                      When you set up the cams as described, did the notches on the right hand side of the cams point inwards towards each other (correct) or outwards away from each other (not correct)?
                      Towards. I'd post a picture if I could.
                      1980 GS550E

                      Comment


                        #12
                        Go buy a spark plug wrench and remove the #4 plug. Put your finger over the hole in the cylinder head and spin over the engine to see if you have any compression. If not, either the valve(s) are open or the cams are timed wrong.

                        Set the crank to 1-4T and then look in the cylinder and make sure the piston crown is at the top of the cylinder.
                        Ed

                        To measure is to know.

                        Mikuni O-ring Kits For Sale...https://www.thegsresources.com/_foru...ts#post1703182

                        Top Newbie Mistakes thread...http://www.thegsresources.com/_forum...d.php?t=171846

                        Carb rebuild tutorial...https://gsarchive.bwringer.com/mtsac...d_Tutorial.pdf

                        KZ750E Rebuild Thread...http://www.thegsresources.com/_forum...0-Resurrection

                        Comment


                          #13
                          As I turned the engine manually, I heard what sounded like a hiss coming from around the left side of the engine.
                          1980 GS550E

                          Comment


                            #14
                            Ok, I do feel compression when I put my thumb over the #4 spark plug hole. But it doesn't feel very strong. Like, not enough to launch a spark plug.
                            1980 GS550E

                            Comment


                              #15
                              Spray some soap water all over the head and cylinders and crank it. If the head gaskets blown youll see bubbles wherever theres an air escape.
                              MY BIKES..1977 GS 750 B, 1978 GS 1000 C (X2)
                              1978 GS 1000 E, 1979 GS 1000 S, 1973 Yamaha TX 750, 1977 Kawasaki KZ 650B1, 1975 Honda GL1000 Goldwing, 1983 CB 650SC Nighthawk, 1972 Honda CB 350K4, 74 Honda CB550

                              NEVER SNEAK UP ON A SLEEPING DOG..NOT EVEN YOUR OWN.


                              I would rather trust my bike to a "QUACK" that KNOWS how to fix it rather than a book worm that THINKS HE KNOWS how to fix it.

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