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78 GS750 engine overhaul on the Cheap!

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    78 GS750 engine overhaul on the Cheap!

    As some of you already know I purchased this 78 GS750 a couple months ago from a seller on FB for $500. The carbs were junk but I still thought there were some good bones to work with. After pulling the oil pan I noticed a lot of condensation had been in the engine for probably 32 years or so. I removed the jugs and found that most of the rings were seized to the pistons. I tried honing the cylinders but the damage was too severe. The rings in #2 & 3 had become part of the cylinder walls. Someone obviously broke them lose before I purchased it.

    The proper fix is to have the cylinders bored .5 mm over and buy pistons and rings. Best case is about $800 using cruzin image piston kits and a qualified machine shop for the boring.
    So that's what I'm going to do..........Later.

    For now, I've purchased a cheap $70 complete gasket kit and 4 used stock pistons, rings and wrist pins for $20 plus $10 postage for All 4 on ebay and I'm going to put this thing together and see what happens. I'm Not going to use any gasket goo or silicone, they will All go on dry. This is a test for me and maybe a few on here. Almost every youtube I watch on engine building they all use some kind of Goo with the gaskets. I'm doing the opposite to see what happens when you use Chinese gasket kits and No Goo. I have to tear it down anyway after I build it.
    Below is the pic of what I bought.

    1977 Suzuki GS750.jpg
    Last edited by Bobbys 94; 02-09-2024, 09:56 PM.
    1978 GS750
    1979 GS750L
    1980 GS550e
    1978 KZ1000
    1975 Honda XL350 K1

    #2
    These are the pistons after the cleaning/ checking specs and stored in a oil bath for 2 weeks.

    IMG_1112.jpg
    1978 GS750
    1979 GS750L
    1980 GS550e
    1978 KZ1000
    1975 Honda XL350 K1

    Comment


      #3
      This is the tedious process of installing the cylinders. Took about and hour to get them on properly.

      IMG_1114.jpg

      1978 GS750
      1979 GS750L
      1980 GS550e
      1978 KZ1000
      1975 Honda XL350 K1

      Comment


        #4
        This is after the safe landing....I Hope.

        IMG_1118.jpg

        1978 GS750
        1979 GS750L
        1980 GS550e
        1978 KZ1000
        1975 Honda XL350 K1

        Comment


          #5
          Waiting on valve seals to finish the head. All valves lapped in nicely.
          Should be in the next couple days. Thanks for watching
          1978 GS750
          1979 GS750L
          1980 GS550e
          1978 KZ1000
          1975 Honda XL350 K1

          Comment


            #6
            If there was water in the sump for years, what condition are the crank bearings in? Rusty bearings are bad ju-ju.
            ---- 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

            Comment


              #7
              Originally posted by Grimly View Post
              If there was water in the sump for years, what condition are the crank bearings in? Rusty bearings are bad ju-ju.
              Wasn't standing water. It was condensation that had built up in the cases. I can only go by what I saw from the top with the cylinders off and pistons removed. All looked normal to me.
              1978 GS750
              1979 GS750L
              1980 GS550e
              1978 KZ1000
              1975 Honda XL350 K1

              Comment


                #8
                My experience with the cheap gasket sets has been OK. The thing to watch is the thickness of the odd shaped O rings at the back corners of the barrel. If they're too thin there's not enough squash to keep them oiltight. A smear of sealant around the outside of those is all I use on the base gasket.
                When stripping an engine if those O rings are in good condition I keep them for possible reuse if the next gasket set has the thin version.

                Comment


                  #9
                  The green base gasket is red flag to me. Athena brand base gaskets are horrible, and almost sure to fail. Hopefully these are better.

                  Regarding the corroded cylinder, I hope it's not as bad as described here. Typically, you can find reasonable condition cylinders off eBay for a decent price.
                  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


                    #10
                    Originally posted by Nessism View Post
                    The green base gasket is red flag to me. Athena brand base gaskets are horrible, and almost sure to fail. Hopefully these are better.

                    Regarding the corroded cylinder, I hope it's not as bad as described here. Typically, you can find reasonable condition cylinders off eBay for a decent price.
                    As I said in my first post, this is a test project. I've looked at the cylinders available on ebay and all the other sources. I could even get a Brand New Factory cylinder from cmsnl if I wanted to for about $700 delivered. This will not be a concours resto.
                    Buying a "Reasonable" cylinder off ebay, I could end up with something worse than what I have to work with now, been there done that. I value all the information I get from the members on this site because as I've said before "I'm no expert" I'm just a guy with time/tools and the love of working on these machines.
                    Last edited by Bobbys 94; 02-09-2024, 09:58 PM.
                    1978 GS750
                    1979 GS750L
                    1980 GS550e
                    1978 KZ1000
                    1975 Honda XL350 K1

                    Comment


                      #11
                      Originally posted by GregT View Post
                      My experience with the cheap gasket sets has been OK. The thing to watch is the thickness of the odd shaped O rings at the back corners of the barrel. If they're too thin there's not enough squash to keep them oiltight. A smear of sealant around the outside of those is all I use on the base gasket.
                      When stripping an engine if those O rings are in good condition I keep them for possible reuse if the next gasket set has the thin version.
                      The O rings you speak of both measured about .010 thicker than the old ones that I removed. No Goo added.
                      1978 GS750
                      1979 GS750L
                      1980 GS550e
                      1978 KZ1000
                      1975 Honda XL350 K1

                      Comment


                        #12
                        Ok, this is certainly interesting. Basically a "I know what I'm doing and I wanna see the minimum amount of work I can get away with to get this running again", right?

                        Though...the engine did see some blasting, did it? No longer in the realm of minimum, then
                        #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


                          #13
                          Originally posted by roeme View Post
                          Ok, this is certainly interesting. Basically a "I know what I'm doing and I wanna see the minimum amount of work I can get away with to get this running again", right?

                          Though...the engine did see some blasting, did it? No longer in the realm of minimum, then
                          Define "Blasting" I'm old and confused. I hope to get it running "Well" and ride her a couple times a week until I die. I've got a donor GS750 coming my way as we speak.
                          Not sure about your "minimum amount of work" comment. I massaged the valve cover for about 6 hours at a minimum.
                          Last edited by Bobbys 94; 02-09-2024, 09:24 PM.
                          1978 GS750
                          1979 GS750L
                          1980 GS550e
                          1978 KZ1000
                          1975 Honda XL350 K1

                          Comment


                            #14
                            The cases look pristine, like they were bead blasted. Or, rattle can painted. Either way, you put in some serious labor. Looks nice. High labor, and low $ outlay?
                            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


                              #15
                              Hope to installed these little bits tomorrow.

                              IMG_1127.jpg
                              Last edited by Bobbys 94; 02-10-2024, 11:45 AM.
                              1978 GS750
                              1979 GS750L
                              1980 GS550e
                              1978 KZ1000
                              1975 Honda XL350 K1

                              Comment

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