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j1 restomod build

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  • #31
    Layout of the exhaust and muffler:
    - Exhaust spacer that fits into the head made from aluminium
    - 1" tubing out of the V2 head (largest I could fit)
    - steps upto 1.25" for the upstyle bend
    - after the bend, exhaust moves into the reverse cone (megaphone) which steps from 1.25" to 3". The reverse cone then steps back down to 1.5"
    - 3" tube was used to make a muffler that joins upto the 3" cone
    - perforated sheet rolled to 1.5" diameter runs inside the 3" tube, with packing in between to create the muffler.
    - muffler was then capped with a 1.5" pie cut tip

    1" stepping upto 1.25" and the aluminium spacer

    Upstyle bend in header pipe

    start of cone/megaphone stepping up from 1.25" to 3"

    cone welded to the header piper



    • #32
      Reverse cones require a sharp taper to create the desired performance of a megaphone. Off the shelf concentric reducers (step up pieces) were too long for the desired effect. I wanted a reverse cone that was only 40mm to step down from 3" to 1.5" so had to fabricate my own.

      To do this, I used an online cone calculator to create a template and cute out the shape from stainless sheet. I then cut the shape into two halves and marked them roughly into eighths. Using a homemade wide faced chisel and a block of hardwood with a groove cut into it, I hit the stainless sheet on the marked lines to slowly bend the two halves into the required shape that i could then weld together.
      I found this process from this youtube video-


      • #33

        Was tempting to leave like this but would have been extremely loud haha


        • #34
          The muffler started with rolling the perforated sheet and tacking together. I flared one end aswell

          Welded a piece of 1.5" tube to the end of the reverse cone for the perforated tube to seat on


          • #35
            The 3" tube covers the perforated tube and reverse cone. Muffler packing was packed in between the perforated tube and 3" tube.
            An exhaust mount and end cap with pie cut tip was welded up


            • #36
              First start, very happy to get to this point!
              First engine I have built entirely myself as well so happy it has no problems (yet).
              Tappets are little loud in the video but have been adjusted



              • #37
                Using an SL70 engine, I later found after I had already assembled the engine that there was no crankcase breather like the z50 engines. Only a small hole in the case between the flywheel and front sprocket was designed as a vent/breather. This would definitely not be upto scratch so I installed a TB breather kit for the v2 head that replaces the inlet tappet cover


                • #38
                  Fantastic fabrication work. Well done!


                  • #39
                    i like it, good job mate.
                    You have two parts of brain, 'left' and 'right'. In the left side, there's nothing right. In the right side, there's nothing left.