Big snag: 850 cylinder block info.

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  • mark
    • Feb 2026
    #1

    Big snag: 850 cylinder block info.

    I've run into a major snag on my '79 850 project.

    My cylinder block needed to be re-bored to the first oversized piston due to a nice big scratch in one of my cylinders.

    The problem is that oversized pistons are no longer available, period. Nothing except a wiseco custom piston. Mimimum 24 run at $150 a piece. Great.

    Perhaps I'm done for, but I suppose I might be able to find another block somewhere with reasonably low miles on it that I could re-hone and use with my original pistons and new rings. At this point I think that's my only option......which seems marginal.

    First question: Are '79-83 cylinder blocks interchangable? This would broaden my options perhaps.

    Second question: This is a total shot in the dark, but if I found a 750 block for my year (or another) a) would it fit? b) could I have it bored to fit my pistons?

    Any other options? I could put in new rings and slap it back together, but this is a pretty nasty scratch and I'd rather not.

    Thanks.
    Tags: None
    • tkent02
      Forum LongTimer
      Past Site Supporter
      • Jan 2006
      • 35571
      • Near South Park
      #2
      I have an 850 cylinder block....

      I was going to put it on my 750 but now I might not get around to it.
      It was in decent shape, I was going to just hone it and slap it on there with some new rings. Have the rest of the top end too if you need anything else. I wouldn't be able to ship it for a little while, it's in Phoenix and I'm not, about a week or so from now I am planning on going down there.
      http://img.photobucket.com/albums/v5...tatesMap-1.jpg

      Life is too short to ride an L.

        Comment

        • mark
          #3
          Originally posted by tkent02
          I was going to put it on my 750 but now I might not get around to it.
          It was in decent shape, I was going to just hone it and slap it on there with some new rings. Have the rest of the top end too if you need anything else. I wouldn't be able to ship it for a little while, it's in Phoenix and I'm not, about a week or so from now I am planning on going down there.
          Wow........that's fast! Top end isn't needed, mine is in good shape. Anyway, I have to get busy here but will get back to you later and see if we can work something out. I'm in no hurry at this point when it comes to the project itself.......

          I just need to make sure what fits and what doesn't.

            Comment

            • 49er
              Forum Sage
              Past Site Supporter
              • Jul 2006
              • 1517
              • Napier, New Zealand
              #4
              Mark
              I had the same problem with my 850 when I stripped it down. It had a deep scratch in one bore. I decided to have some custom pistons made at 71mm and 10.5 to 1. It's the best decision I've made on my setup. I takes the capacity to 893cc. The extra punch through the rev range is great. Everythings standard on my bike except the 4-1 exhaust, and now of course the pistons.
              Give John Noonan a call at JE Pistons. He did my set of pistons, rings, pins and circlips for US$680. If you don't radically change your cam lift or valve sizes you will be able to use the same pistons in your motor. PM me if you have any other questions.
              Cheers
              Ian
              :) The road to hell is paved with good intentions......................................

              GS 850GN JE 894 10.5-1 pistons, Barnett Clutch, C-W 4-1, B-B MPD Ignition, Progressive suspension, Sport Demons. Sold
              GS 850GT JE 1023 11-1 pistons. Sold
              GS1150ES3 stock, V&H 4-1. Sold
              GS1100GD, future resto project. Sold

              http://i155.photobucket.com/albums/s...s/P1000001.jpg
              http://i155.photobucket.com/albums/s...s/P1000581.jpg

                Comment

                • rphillips
                  Forum Guru
                  Past Site Supporter
                  Super Site Supporter
                  • Jun 2005
                  • 7612
                  • Norene TN
                  #5
                  How about changing, just the bad sleeve, any old "cheeeep" 850 block you find should have at least 1 good sleeve.
                  1983 GS1100E, 1983 CB1100F, 1991 GSX1100G, 1996 Kaw. ZL600 Eliminator, 1999 Bandit 1200S, 2005 Bandit 1200S, 2000 Kaw. ZRX 1100

                    Comment

                    • mark
                      #6
                      Well, hate to bump this to the top, but it turns out that oversized 850 OEM pistons and rings ARE still available. I guess the fact that they are sold as a set (pistons and rings together) rather than seperately is odd and confusing for the parts guys.

                      So if you need them, they are still out there at least for now.

                        Comment

                        • first timer
                          Forum Sage
                          • Aug 2002
                          • 3429
                          • Tucson, Arizona
                          #7
                          for the cost of oem stuff it would probly cost as much to do the above mentioned custom kit.

                          plus you could get some extra rings made so you'll have a extra set
                          78 GS1000 Yosh replica racer project, 82 Kat 1000, 10 990 ADV-R, Some dirt bikes

                            Comment

                            • mark
                              #8
                              Actually, first oversize OEM pistons and rings are $64.0 a set x 4 (through Z1enterprises), plus wrist pins as opposed to $170 a set x 4 for the custom ones (pistons, rings, pins, clips). That's quite a bit less. The custom ones are nicer of course, but for my application OEM is all I'll ever need or want.

                              Ian's set up sounds nice though.

                                Comment

                                • Kcwiro
                                  #9
                                  Yeah know what you mean on the pistons.... I busted a ring on my project 750... and only way for me to get another one was to order another set of piston to replace the one I messed up.... very wierd....

                                  I'm still waiting on backorder atm but once it comes in I am getting the correct tool to avoid my issue reoccuring.... then I'm golden =)

                                  Good luck on your 850

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