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DT125R FORUM

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Piston rings

Scheduled Pinned Locked Moved Top End
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  • markus.wM markus.w

    @declan I just checked the Haynes manual and it says that only the 3db 1988 round slide carb model was 56.4 then the 1989 3rn1 onwards is 56.0 so seems like you got the rare early model or at least the early engine/barrel.

    declanD Offline
    declanD Offline
    declan
    wrote on last edited by declan
    #8

    @markus-w maybe, my barrel is stamped 3mb though I'm not too knowledgeable on engine codes I'll just have to keep looking around I'll probably just have to get a whole piston kit

    declanD markus.wM 2 Replies Last reply
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    • declanD declan

      @markus-w maybe, my barrel is stamped 3mb though I'm not too knowledgeable on engine codes I'll just have to keep looking around I'll probably just have to get a whole piston kit

      declanD Offline
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      declan
      wrote on last edited by
      #9

      My theory is the shop that handled my barrel work or a previous owner thought it was a tzr barrel and pressed in a tzr cylinder liner (providing the ports match) and that's why the dtr pistons don't match but the tzr ones do

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      • declanD declan

        @markus-w maybe, my barrel is stamped 3mb though I'm not too knowledgeable on engine codes I'll just have to keep looking around I'll probably just have to get a whole piston kit

        markus.wM Offline
        markus.wM Offline
        markus.w
        wrote on last edited by
        #10

        @declan they all say 3MB it's the first digits of the engine/frame number you need for ordering parts. It will start with 3DB if it is the early 56.4mm bore or 3MD from 89-96 and 96 onwards is 4BL. That's presuming you got the original barrel but if it 56.4 then it is a 3DB.

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        • markus.wM markus.w

          @declan they all say 3MB it's the first digits of the engine/frame number you need for ordering parts. It will start with 3DB if it is the early 56.4mm bore or 3MD from 89-96 and 96 onwards is 4BL. That's presuming you got the original barrel but if it 56.4 then it is a 3DB.

          declanD Offline
          declanD Offline
          declan
          wrote on last edited by
          #11

          @markus-w my frame number starts with 3md

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          • declanD declan

            @markus-w my frame number starts with 3md

            declanD Offline
            declanD Offline
            declan
            wrote on last edited by declan
            #12

            @declan and that's supposed a 1990 or atleast it's registered as such

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            • declanD declan

              @declan and that's supposed a 1990 or atleast it's registered as such

              markus.wM Offline
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              markus.w
              wrote on last edited by
              #13

              @declan sounds right as 3MD is 89-96 so your barrel has probably been changed somewhere along the line.

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              • declanD declan

                Hi, so I'm in the market for some piston rings, pjme has the ones I like genuine RIK rings but they list the stock bore as 56.00 my stock bore if memory serves is 56.40 and I have a .50 rebore so I need 56.90 but the. 50 over rings on pjs don't match my bore since the standard bores are different between mine and theirs, so does anyone have a link to some good quality none OEM rings that suit a 56.90 mitaka piston for around 20 pound pjs rings are 17 pound which is quite cheap

                S Offline
                S Offline
                SpookDog
                wrote on last edited by
                #14

                @declan
                Have you talked to PJME? If you have a 3mb barrel it was never fitted with a 56.5 piston. A 3bn oversize will fit them both as the piston skirt and porting is the same. As far as I know 🙂

                declanD 1 Reply Last reply
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                • S SpookDog

                  @declan
                  Have you talked to PJME? If you have a 3mb barrel it was never fitted with a 56.5 piston. A 3bn oversize will fit them both as the piston skirt and porting is the same. As far as I know 🙂

                  declanD Offline
                  declanD Offline
                  declan
                  wrote on last edited by
                  #15

                  @spookdog nah I didn't talk to them, I've ordered a piston from yam bits to suit my barrel size it's for pre 90s bikes it should work I'll compare them before fitting just in case it arrives tomorrow so I'll keep the thread updated over the weekend

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                  • declanD declan

                    @spookdog nah I didn't talk to them, I've ordered a piston from yam bits to suit my barrel size it's for pre 90s bikes it should work I'll compare them before fitting just in case it arrives tomorrow so I'll keep the thread updated over the weekend

                    declanD Offline
                    declanD Offline
                    declan
                    wrote on last edited by
                    #16

                    The piston works it was a piston for pre 89 dt125rs from yam bits, the bike has a lot of felt compression now seems way more than it had when it originally had a rebore and piston making me wonder if the rings were defective from new on the original piston, i did tighten the squish up just a tad with a slightly thinner gasket but I highly doubt that's the reason for the increase in compression before the kickstarter had litteraly no fight back on your foot or hand and it was like that the whole time I rode it.

                    declanD 1 Reply Last reply
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                    • declanD declan

                      The piston works it was a piston for pre 89 dt125rs from yam bits, the bike has a lot of felt compression now seems way more than it had when it originally had a rebore and piston making me wonder if the rings were defective from new on the original piston, i did tighten the squish up just a tad with a slightly thinner gasket but I highly doubt that's the reason for the increase in compression before the kickstarter had litteraly no fight back on your foot or hand and it was like that the whole time I rode it.

                      declanD Offline
                      declanD Offline
                      declan
                      wrote on last edited by declan
                      #17
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                      declanD 1 Reply Last reply
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                      • declanD declan

                        This post is deleted!

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                        declan
                        wrote on last edited by
                        #18
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