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Pistons #1 and #4 lodged on reinstall

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    #1

    Pistons #1 and #4 lodged on reinstall

    On my GS850 rebuild...

    Okay, I messed up pretty bad here. After putting new piston rings on and lightly honing the cylinders, I was putting the jugs back on. I rotated #2 and #3 up and got them in without much trouble, then I slid the cylinders down further to #1 and #4 and got the rings started in the bottom of the cylinders, but they were tougher to get in. Long story short, I resorted to tapping with a mallet on the cylinder block to get it seated and I now realize that was a big mistake.

    Fast forward, the #1 and #4 pistons are lodged firmly in their cylinders and I can't seem to get them unstuck, no matter what I try. I'm guessing they're misaligned in there and that's why they're stuck. I'm afraid to use any more force on them for fear of irreparably damaging the cylinders (I know the pistons may be unsalvageable at this point). Even if I wanted to try to get at them from the underside, I'm not sure how because these piston rods don't come apart and it looks like it's not even possible to disassemble the crankshaft with the #1 and #4 pistons engaged.

    Sorry guys, I don't mess up like this very often and I think this is the worst I've messed up on a vehicle I've worked on. I should have known better than to use any force at all on reinstall, but I got too eager to get it back together.

    Is there anything I can try at this point? Or am I looking at getting another engine altogether here?
    Tags: None
    #2
    Can you get to the wrist pins still? Remove the circle clip wire and lift pistons off with the cylinders. Bet you'll find one of the thin rings on the oil control rings has wedged itself. A block of wood should smack the piston out. It's happened to me. There was a little nick on my piston but it filed right off. These things rings can be a pain to get in at times...this my asking for ring compressor suggestions a while ago. My fat fingers are a hindrance and not a help
    Last edited by chuck hahn; 09-03-2020, 11:43 AM.
    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.

    Comment

      #3
      Might be a mark on the liner too. Might have to run a ball hone to freshen it up. Hopefully it doesn't dig into the liner. If a mark is below the area the piston will travel I don't see any reason to do anything than sand it smooth so it won't snag rings when putting cylinders on.
      Last edited by chuck hahn; 09-03-2020, 11:49 AM.
      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.

      Comment

        #4
        Originally posted by chuck hahn View Post
        Can you get to the wrist pins still?
        Unfortunately no, they're too far up in there to get to them. I've tried a block of wood from the top, but even then I get nominal progress (like 0.1mm, I measured it with the tail of a digital caliper) I'm afraid if I smack any harder on the top of the pistons it will just dig in more.

        Comment

          #5
          Well. As I see it, you've gotta do what ya gotta do. 2X2 dead center of the piston and put wood under the bottom of jugs and have at it.
          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.

          Comment

            #6
            Originally posted by chuck hahn View Post
            Well. As I see it, you've gotta do what ya gotta do. 2X2 dead center of the piston and put wood under the bottom of jugs and have at it.
            Yeah, I'm coming to that conclusion myself. If the only other option is another engine, what do I have to lose? I'll give it a try and report back. Thanks!

            Comment

              #7
              I had a similar problem. In getting it loose, I busted a piece off of one of the piston skirts. No other damage. Bought a used piston off of e-bay for $10. That was over 5000 miles ago.

              1983 GS750ED-Horsetraded for the Ironhead
              1981 HD XLH

              Drew's 850 L Restoration

              Drew's 83 750E Project

              Comment

                #8
                Yeah....is what it is now.
                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.

                Comment

                  #9
                  This is not an uncommon occurrence.
                  Last year I did almost the same, but just as they started to go cock-eyed and jam I recalled the last time that happened and stopped. They weren't stuck by much, so I was able to put a piece of 2x2 down from the top and whack the cocked side of the piston to attempt to right its alignment. Resist the temptation to clout the piston skirt, but it will show you what part of the piston crown to attack.
                  It will also help to put a broomstick under the barrels and exert some upward force, just be careful to not destroy the base gasket.
                  Once it's out, dismantle it again and check for damage.
                  Last edited by Grimly; 09-03-2020, 05:04 PM.
                  ---- 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

                    #10
                    Great news! I was able to drive both pistons back out the bottom of the cylinder liners. Chuck called it, both of them had oil rings folded downwards. This is the #1 piston which was the hardest to drive out.

                    7F5AB570-82D3-4D7E-B7C8-00EC8899B1DC.jpg

                    After looking over the damage, I think I can file down the rough spots on the pistons and hone down the cylinders. There’s just minor surface scratches on all parts involved.

                    Thanks for the support and encouragement!

                    One more note for others who might read this. Measuring the position depth with the tail of a digital caliper made this a lot easier to tell if I was making progress and which side was higher or lower.

                    Comment

                      #11
                      Congrats & thank goodness for no major damage.
                      1983 GS1100E, 1983 CB1100F, 1991 GSX1100G, 1996 Kaw. ZL600 Eliminator, 1999 Bandit 1200S, 2005 Bandit 1200S, 2000 Kaw. ZRX 1100

                      Comment

                        #12
                        learning a valuable lesson here eh? you'll get there
                        1983 GS 1100 ESD

                        Comment

                          #13
                          Originally posted by greg78gs750 View Post
                          learning a valuable lesson here eh? you'll get there
                          Definitely. I'm just glad the lesson wasn't more expensive. I just ordered another set of piston rings and a base gasket from PartsOutlaw, which I feel isn't very costly in comparison to what it could have been!

                          Comment

                            #14
                            Just out of curiosity, did you clean the carbon out of the ring grooves before you installed the new rings???

                            Comment

                              #15
                              Originally posted by rapidray View Post
                              Just out of curiosity, did you clean the carbon out of the ring grooves before you installed the new rings???
                              Yeah, there wasn't much carbon in any of the grooves to begin with, especially the oil ring groove. I think I just didn't have the oil rings compressed enough and forced them in.

                              Comment

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