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  4. CB750 scrambler project

CB750 scrambler project

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  • S SpookDog

    You mean the hole at 9 o’clock on the pic? Yeah, it could be oil bathed. Specially if the cover had a oil proof gasket. 4 strokes are ‘different’ 😜
    I’d look into the voltage issue.

    Louis-DT-WRL Offline
    Louis-DT-WRL Offline
    Louis-DT-WR
    wrote on last edited by
    #104

    @SpookDog yes I think my main concerns now is why is there so much pressure in the crankcase? Manual said 3.5L oil with a new filter..... I wonder if it's wrong and over filled

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    • Louis-DT-WRL Offline
      Louis-DT-WRL Offline
      Louis-DT-WR
      wrote on last edited by
      #105

      Right, I thought "oh shit the crank seal is gone"

      Looking at all diagrams..there isn't a seal!
      Anyone else who wants to help confirm I'm not going made... Please do 🙂

      The oil literally returns to the sump through that window where you can see the crankshaft web.... Strange right... But makes sense why there's a "return" to the sump
      The side cover is a sealed type so that's why oil doesn't drip out.

      The oil is about 0.5l -.6L over filled from having the wrong information in a manual I have..

      Manual states oil capacity (when replaced) 2.8L without filter and 3L with filter. (Dipstick still doesn't show anything... Perhaps from another bike)

      I believe this caused there to be oil on the pulse generator = no pick up pulse.....

      Drain the oil time tomorrow. Refill to correct level.

      Clean up pulse generator... If still not producing 0.7v I need a new one.

      🤞 This is the issue.

      1 Reply Last reply
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      • S Offline
        S Offline
        SpookDog
        wrote on last edited by
        #106

        4 strokes always have air movement in the case/block, the pistons pumping up and down displace air. You can get over pressure from worn rings/ piston blow-by...
        You ain’t going mad, sanity is just a learning curve 🤪

        Louis-DT-WRL 1 Reply Last reply
        1
        • S SpookDog

          4 strokes always have air movement in the case/block, the pistons pumping up and down displace air. You can get over pressure from worn rings/ piston blow-by...
          You ain’t going mad, sanity is just a learning curve 🤪

          Louis-DT-WRL Offline
          Louis-DT-WRL Offline
          Louis-DT-WR
          wrote on last edited by
          #107

          @SpookDog I think actually how this works now
          Apparently the pulse generator is supposed to have oil in there (oil cooled)... Which is great because there is no oil seal on the crankshaft that can go wrong......

          If you remove the cover when it's on the side stand (the only Stand I have)lots of oil will pour out...
          Only a small amount of oil come out on the centre stand....
          The pulse generator seems to not put out enough voltage so I've ordered a new one.

          As I've done lots of tests it is is the pulse generator that I believe is the issue.

          There's also supposed to be a proper gasket for the cover which I've ordered

          The CBX 750 which is almost an identical engine have the oil filler cap on the left-hand side.

          As the cbx750 shares a lot of parts
          On my bike this has a cap saying "do not open"
          On the left casing (where the oil filler is on the CBX)

          if you open this when it's on the side stand oil will pour out as well..

          . I'm guessing at the CBX 750 at the side stand on the right hand side.

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          • S Offline
            S Offline
            SpookDog
            wrote on last edited by
            #108

            I had a gsxr750 that was the same, oil cooled, 2 oil caps, total bitch to diagnose 😊

            Louis-DT-WRL 1 Reply Last reply
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            • S SpookDog

              I had a gsxr750 that was the same, oil cooled, 2 oil caps, total bitch to diagnose 😊

              Louis-DT-WRL Offline
              Louis-DT-WRL Offline
              Louis-DT-WR
              wrote on last edited by
              #109

              @SpookDog it's not even mentioned in the manual about not removing the left-hand pulse generator cover on the sidestand 🤷‍♂️

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              • Louis-DT-WRL Offline
                Louis-DT-WRL Offline
                Louis-DT-WR
                wrote on last edited by
                #110

                I have no idea when I use the shrug emoji it changes it to a girl and the gender symbol 😂

                After further investigation... My cdi which was sold by a bike breaker written in white paint "cb750 1997" ... I cleaned off the paint carefully and the part number just about readable is

                MASG G
                571U

                Which is a cbr900!!!

                Whether or not that's a problem, I've got another one from another spares breaker with the correct part number for the cb750 sevenfifty

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                • CalumC Offline
                  CalumC Offline
                  Calum
                  wrote on last edited by
                  #111

                  Keep us posted! I'm itching to hear that you've cracked this!

                  Always Originate, Never Pirate!

                  Louis-DT-WRL 1 Reply Last reply
                  0
                  • CalumC Calum

                    Keep us posted! I'm itching to hear that you've cracked this!

                    Louis-DT-WRL Offline
                    Louis-DT-WRL Offline
                    Louis-DT-WR
                    wrote on last edited by
                    #112

                    Same here. Should be beasty.
                    I knew the electrics would be the hardest part.
                    All lights and horn was easy.
                    Starter circuit was ok.
                    Just the ignition circuit 😁

                    1 Reply Last reply
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                    • S Offline
                      S Offline
                      SpookDog
                      wrote on last edited by
                      #113

                      It WILL fire up with a new CDI, unfortunately online buying is a fukin shark feeding frenzy of a$$hol£s all caring about one thing. The amount of times I’ve been shafted on fleabay is unreal. Brought a headlight that came without the bulb holder or rubber, the bloke had the neck to tell me that I was confusing his with another listing, conveniently after his pics were down. The only reason I nodded was cause it was complete...
                      Another bloke changed the listing twice while I was between messaging. Once to up the price £40 then to change from 3 wire to 5wire servo! Same listing number an all...

                      Louis-DT-WRL 1 Reply Last reply
                      1
                      • S SpookDog

                        It WILL fire up with a new CDI, unfortunately online buying is a fukin shark feeding frenzy of a$$hol£s all caring about one thing. The amount of times I’ve been shafted on fleabay is unreal. Brought a headlight that came without the bulb holder or rubber, the bloke had the neck to tell me that I was confusing his with another listing, conveniently after his pics were down. The only reason I nodded was cause it was complete...
                        Another bloke changed the listing twice while I was between messaging. Once to up the price £40 then to change from 3 wire to 5wire servo! Same listing number an all...

                        Louis-DT-WRL Offline
                        Louis-DT-WRL Offline
                        Louis-DT-WR
                        wrote on last edited by
                        #114

                        @SpookDog I know the feeling. Many sellers have lots of similar items for sale but send the wrong ones.
                        The problem is I built this bike with parts from about 30 bikes... And no real way to test it will work together until I try

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                        • Louis-DT-WRL Offline
                          Louis-DT-WRL Offline
                          Louis-DT-WR
                          wrote on last edited by
                          #115

                          I've got sparks on the plugs.... Just need 1 more part before I start up.... 💪

                          1 Reply Last reply
                          1
                          • Louis-DT-WRL Offline
                            Louis-DT-WRL Offline
                            Louis-DT-WR
                            wrote on last edited by
                            #116

                            She runs and runs beautiful!
                            I'll do a video when fully warmed up.
                            And not pouring rain.

                            It was screeching when I started it., Originally thought it was the starter, but when running it was awfully loud. I thought "here we go" something major.
                            I had a suspicion it was the generator....
                            Look what I found...
                            A tiny recess where a slightly bent fan blade was rubbing the cover.

                            Really easy fix and now sounds great!

                            alt text

                            alt text

                            alt text

                            1 Reply Last reply
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                            • S Offline
                              S Offline
                              SpookDog
                              wrote on last edited by
                              #117

                              Congrats bud! I thought it be painless in the end...

                              Louis-DT-WRL 1 Reply Last reply
                              1
                              • S SpookDog

                                Congrats bud! I thought it be painless in the end...

                                Louis-DT-WRL Offline
                                Louis-DT-WRL Offline
                                Louis-DT-WR
                                wrote on last edited by
                                #118

                                @SpookDog cheers , and thanks for following everyone. Some final cosmetic touches and possibly rejetting left to do 💪
                                Can't believe how fast and smoothly it revs up

                                NINJAN 1 Reply Last reply
                                1
                                • Louis-DT-WRL Offline
                                  Louis-DT-WRL Offline
                                  Louis-DT-WR
                                  wrote on last edited by
                                  #119

                                  Have a little listen 😝 ears are bleeding 😂

                                  https://youtu.be/3E1flO9j7BA
                                  link text

                                  1 Reply Last reply
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                                  • CalumC Offline
                                    CalumC Offline
                                    Calum
                                    wrote on last edited by
                                    #120

                                    Haha! Ruthless!

                                    Always Originate, Never Pirate!

                                    1 Reply Last reply
                                    1
                                    • Louis-DT-WRL Louis-DT-WR

                                      @SpookDog cheers , and thanks for following everyone. Some final cosmetic touches and possibly rejetting left to do 💪
                                      Can't believe how fast and smoothly it revs up

                                      NINJAN Offline
                                      NINJAN Offline
                                      NINJA
                                      wrote on last edited by
                                      #121

                                      @Louis-DT-WR BRAP BRAP BRAP, sounds beastly dude!!!

                                      SEDUCED BY THE DARK SIDE!!!

                                      Louis-DT-WRL 1 Reply Last reply
                                      1
                                      • NINJAN NINJA

                                        @Louis-DT-WR BRAP BRAP BRAP, sounds beastly dude!!!

                                        Louis-DT-WRL Offline
                                        Louis-DT-WRL Offline
                                        Louis-DT-WR
                                        wrote on last edited by
                                        #122

                                        @NINJA it is very beastly sounding if I say so😁 I didn't know what to expect. Definitely will wear ear defenders next time

                                        1 Reply Last reply
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                                        • CalumC Offline
                                          CalumC Offline
                                          Calum
                                          wrote on last edited by
                                          #123

                                          I know it's not the same, but my RS is too loud for prolonged use without ear plugs. My ears are literally ringing from the noise. I am a sensitive lad though.

                                          Always Originate, Never Pirate!

                                          Louis-DT-WRL 1 Reply Last reply
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