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  4. 4bl (3mb0?) cylinder with a 3bn head?

4bl (3mb0?) cylinder with a 3bn head?

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  • markus.wM markus.w

    @SpookDog tell me please, I know the bore and stroke are slightly different sizes but what would be the consequences of fitting the later barrel to the early crank? Other than maybe changing performance slightly would it cause any harm?

    S Offline
    S Offline
    SpookDog
    wrote on last edited by SpookDog
    #11

    @markus-w

    You would only be down on compression. The real problem would be putting a 3bn barrel on a later engine because the stroke of the crank/piston would be longer than the barrel and smack into the head...

    The 3bn barrel wasn’t even a whole year model was it? My 1988 DTR125 has a 3mb barrel and crank...

    Didn’t the TZR use 3mb barrels? I know I’ve used the TZR pistons in my 3mb Dtr as oversized. I’m not well versed in the history...

    I wonder it the ‘R’ was for revised? Definitely wasn’t for race!...

    markus.wM 1 Reply Last reply
    0
    • B Bavarian

      @SpookDog @markus-w The engine/frame number is 3DD000350, I think it's a Swiss import. Both cylinder and the head are 3BN

      HOTSHOT IIIH Offline
      HOTSHOT IIIH Offline
      HOTSHOT III
      wrote on last edited by
      #12

      @Bavarian I just looked your VIN up on Yamaha France and your bike is 100% an early 3DD1 model (sold as a 3BN in the UK); 56.4 x 50.0mm bore and stroke, VM26SS round slide carb and different electrics including a separate YPVS controller on top of the airbox.

      So if you were going to fit a later crankshaft and cylinder you might end up needing a TM28SS flatslide carb and different stator, loom and CDI unit to fully convert it. Is your original cylinder serviceable?

      Take a look here: https://www.yamaha-motor.eu/fr/fr/service-maintenance/parts-catalogue/#/

      1 Reply Last reply
      2
      • S SpookDog

        @markus-w

        You would only be down on compression. The real problem would be putting a 3bn barrel on a later engine because the stroke of the crank/piston would be longer than the barrel and smack into the head...

        The 3bn barrel wasn’t even a whole year model was it? My 1988 DTR125 has a 3mb barrel and crank...

        Didn’t the TZR use 3mb barrels? I know I’ve used the TZR pistons in my 3mb Dtr as oversized. I’m not well versed in the history...

        I wonder it the ‘R’ was for revised? Definitely wasn’t for race!...

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

        @SpookDog the Haynes manual says the tzr used the 56.4/50 3bn up to 1996. I did once read that the r was for replica, being a replica of the tz race bikes hence tz replica.

        MadGyverM 1 Reply Last reply
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        • markus.wM markus.w

          @SpookDog the Haynes manual says the tzr used the 56.4/50 3bn up to 1996. I did once read that the r was for replica, being a replica of the tz race bikes hence tz replica.

          MadGyverM Offline
          MadGyverM Offline
          MadGyver
          wrote on last edited by
          #14

          I would like to add my 2 cent's.I have 3MB and 2RH(=3BN) cylinders,I've measured them off the bike and on the 3BN00 cases from my 4BL bike,and everything is the same,I think on '88 DT's and early TZR the less 0.7mm is on the crankcase side not the cylinder..

          I need my tools and a pile of junk.....

          CalumC S markus.wM 3 Replies Last reply
          3
          • MadGyverM MadGyver

            I would like to add my 2 cent's.I have 3MB and 2RH(=3BN) cylinders,I've measured them off the bike and on the 3BN00 cases from my 4BL bike,and everything is the same,I think on '88 DT's and early TZR the less 0.7mm is on the crankcase side not the cylinder..

            CalumC Offline
            CalumC Offline
            Calum
            wrote on last edited by
            #15

            @MadGyver That's really useful to know actually, I just assumed it would be from the cylinder...

            Always Originate, Never Pirate!

            1 Reply Last reply
            0
            • MadGyverM MadGyver

              I would like to add my 2 cent's.I have 3MB and 2RH(=3BN) cylinders,I've measured them off the bike and on the 3BN00 cases from my 4BL bike,and everything is the same,I think on '88 DT's and early TZR the less 0.7mm is on the crankcase side not the cylinder..

              S Offline
              S Offline
              SpookDog
              wrote on last edited by
              #16

              @MadGyver

              So, ignore the previous conception that 3bn and 3mb aren’t compatible? It makes no difference what goes on what? If that’s right it’s definitely good to know...

              1 Reply Last reply
              0
              • CalumC Offline
                CalumC Offline
                Calum
                wrote on last edited by
                #17

                @spookdog well not compatible on a DTR at least...

                Always Originate, Never Pirate!

                1 Reply Last reply
                0
                • MadGyverM MadGyver

                  I would like to add my 2 cent's.I have 3MB and 2RH(=3BN) cylinders,I've measured them off the bike and on the 3BN00 cases from my 4BL bike,and everything is the same,I think on '88 DT's and early TZR the less 0.7mm is on the crankcase side not the cylinder..

                  markus.wM Offline
                  markus.wM Offline
                  markus.w
                  wrote on last edited by
                  #18

                  @MadGyver obviously the .7mm difference in stroke would be acquired by altering the crankshaft as that's the only possible way to alter the stroke, but you're saying they both use the exact same cylinder dimensions? Did you measure the port heights because that is where we'd see these possible differences?

                  MadGyverM 1 Reply Last reply
                  1
                  • markus.wM markus.w

                    @MadGyver obviously the .7mm difference in stroke would be acquired by altering the crankshaft as that's the only possible way to alter the stroke, but you're saying they both use the exact same cylinder dimensions? Did you measure the port heights because that is where we'd see these possible differences?

                    MadGyverM Offline
                    MadGyverM Offline
                    MadGyver
                    wrote on last edited by MadGyver
                    #19

                    @markus-w I had put the cylinder of a TZR125 2RH on my DTR,complete with piston using the DT's stock base gasket,did not mount the head.I wanted to take measurements to make a custom gasket in case I was going the TZR way and not the Athena170. Everything aligned like the stock,piston bdp was same level with the ports floor and at tdp was level with the cylinder.Put it out and started measuring the height of the cylinder and was the same with my 3MB and the Athena. Didn't do a full port map.

                    @Calum I didn't have 2RH crankcases to do the reverse measuring.I assumed that the 0.7 is from the cases.
                    I had the belief like everyone that was from the cylinder.

                    I need my tools and a pile of junk.....

                    B 1 Reply Last reply
                    1
                    • MadGyverM MadGyver

                      @markus-w I had put the cylinder of a TZR125 2RH on my DTR,complete with piston using the DT's stock base gasket,did not mount the head.I wanted to take measurements to make a custom gasket in case I was going the TZR way and not the Athena170. Everything aligned like the stock,piston bdp was same level with the ports floor and at tdp was level with the cylinder.Put it out and started measuring the height of the cylinder and was the same with my 3MB and the Athena. Didn't do a full port map.

                      @Calum I didn't have 2RH crankcases to do the reverse measuring.I assumed that the 0.7 is from the cases.
                      I had the belief like everyone that was from the cylinder.

                      B Offline
                      B Offline
                      Bavarian
                      wrote on last edited by
                      #20

                      Thanks everyone! That's very useful information for me.

                      @MadGyver so does that mean 3MB will possibly work on 3BN engine with shorter stroke?
                      Perhaps the difference on the stroke comes from the connecting rod? Could that 0.7mm difference in stroke cause a significant performance drop?

                      My barrel still has some life in it although it has been resleeved and sleeve quality doesn't look that good. But I want to buy another one for spare and to play with 😄
                      It seems it's quite difficult to find a 3BN one.

                      1 Reply Last reply
                      0
                      • OllieDTRO Offline
                        OllieDTRO Offline
                        OllieDTR
                        wrote on last edited by
                        #21

                        Hi guys I’ve got a 3BP bottom end, does anyone know what year it is and what crank stroke does it have? As want to run a 3MB barrel thanks!

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