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Bros 900 4 Valve / EFI

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  • Bros 900 4 Valve / EFI

    People may remember the thread elsewhere on the forum where I’ve been writing about my creation of a Frankenstein’s monster type engine involving the 4 valve per cylinder top end from a Deauville NT700-V engine, the bottom end from a XRV750 Africa Twin and some big bore pistons to take the thing out to nearly 900cc.

    I had originally thought I’d eventually put this motor in my existing 1988 Bros/XRV750 but have decided to instead build a second bike for the 900cc motor. This way, I can have the 750 for riding around on and can use this new one as the test bed for any wild ideas that might come to me.

    It will be a while before I can start the build proper, as I’m in the midst of gradually moving and I need to build a new workshop at the new place. I’m in the process of clearing some ground for that and hope that the workshop will be up and all my tools and bike stuff will be here by the end of 23.

    In the meantime, I’ve started accumulating bits and pieces and have got most of the big stuff now - frame; MK2 wheels; ZXR400 forks; 6 piston Tokico caliper; Koso multifunction instrument (etc.)

    Some of the things I’m thinking of making/incorporating:
    Homemade carbon fibre fuel tank and belly pan
    Aprilia RS250 carbon fairing (top only), with 50mm ‘projector’ type headlight and air-intake ducting in aluminium or carbon
    Honda RS125 racing seat.
    Honda NSR250 radiator
    NT700V EFI system
    Homemade underslung bracket for HEL rear caliper
    Cushless rear hub (to allow smaller sprockets to be fitted, if desired.
    Homemade aluminium subframe
    Homemade high level exhaust (NT700V heads won’t take the usual NT650 Hawk/Bros pipes)
    Homemade rearsets
    Home modified carbon clip-ons

    That’s as much as I can recall for now.

    Anyway, although I can’t start the build proper for a bit, I can continue accumulating the parts and know-how needed, hence this build thread to harvest the collective wisdom of the forum

    I should also make quite clear that - in the best traditions of bike building - this is all highly impractical and a waste of money but may offer some kind of warped pleasure on the way

    5853C8EA-CC1B-437E-AAED-066C365F4E33.jpg 5DE6C0E8-2380-4F48-AABB-7000A3139E23.jpg

  • #2
    Excellent idea. Looking forward to your updates.

    Comment


    • #3
      Looking forward to it.

      Comment


      • #4
        I was fascinated by your first project and in awe of your mechanical prowess so this one will certainly be worth following. All the best with it

        Comment


        • #5
          be sure to post a video of it running......................if it ever does.

          "It's only getting worse."


          MY rides: '97 VFR750, '90 Red Hawk, '88 Blue/Black Hawk, '86 RWB VFR700 (3), '86 Yamaha Radian, '90 VTR250, '89 VTR250 (2), '73 CB125, '66 Yamaha YL-1

          Sold: '86 FJ1200, '92 ZX-7, '90 Radian, '73 CB750, '89 all-white Hawk, '88 blue Hawk, '86 FZ600, '86 Yam Fazer 700 , '89 VTR250, '87 VFR700F2, '86 VFR700F.

          Comment


          • #6
            Originally Posted by squirrelman
            be sure to post a video of it running......................if it ever does.
            Will do!

            You may be crediting me with being more ambitious than I actually am. All the most difficult stuff is already done by Mr Honda, so its mostly a question of putting the bits together in the right order. Probably easier than my dry clutch conversion and there is a video of that… running

            Comment


            • #7
              OK, carry on sir, your project is inspiring, but as a lazy skeptic without a machine shop or the brains to run one, gotta ask why not just buy a newer, better bike and avoid the countless modification hours and grinding time and the need to dial in FI with a new setup entirely and have a bike off the road for a few years, waiting for technical developments?

              so many bike choices now, so many improvements from the mid-eightys hawk design.
              Last edited by squirrelman; 05-05-2023, 09:07 PM.
              "It's only getting worse."


              MY rides: '97 VFR750, '90 Red Hawk, '88 Blue/Black Hawk, '86 RWB VFR700 (3), '86 Yamaha Radian, '90 VTR250, '89 VTR250 (2), '73 CB125, '66 Yamaha YL-1

              Sold: '86 FJ1200, '92 ZX-7, '90 Radian, '73 CB750, '89 all-white Hawk, '88 blue Hawk, '86 FZ600, '86 Yam Fazer 700 , '89 VTR250, '87 VFR700F2, '86 VFR700F.

              Comment


              • #8
                Originally Posted by squirrelman
                OK, carry on sir, your project is inspiring, but as a lazy skeptic without a machine shop or the brains to run one, gotta ask why not just buy a newer, better bike and avoid the countless modification hours and grinding time and the need to dial in FI with a new setup entirely and have a bike off the road for a few years, waiting for technical developments?

                so many bike choices now, so many improvements from the mid-eightys hawk design.
                The answer is quite simple - I enjoy making things - its a passion, I suppose.

                To be honest, while I do enjoy riding motorbikes, and have been doing so more than 40 years, creativity is probably an even greater source of pleasure.

                Comment


                • #9
                  Besides making things, I also enjoy shopping; slumped here on the sofa chasing down parts from across the world, causing the postman to come up the track to this remote cottage with parcels to unwrap .

                  Currently, I’m debating whether to get a Jetprime programmable control unit for the EFI.

                  9A312A5F-3098-4789-A652-0B8BF03071CC.jpg

                  Compared to other forum members work to fit injection to the Hawk engine, I’ve got it easy. Basically, because I’m using the NT700V top end I can transfer the entire EFI set up to my XRV bottom end: cam position sensor, intake stubs, ECU, etc - it all fits straight on. It also seems that the XRV crank and crank cases have provision for the NT700V ignition trigger to be fitted on the clutch side of the crank. Although the XRV has the ignition sensors on the other side of the engine, on the flywheel, the crankcases on the other side are drilled to accept the sensor and have a blanked off hole for the wire.

                  I’ve got the NT700V injectors, sensors, ECU and whole wiring loom and plan to fit that all, to at least have a starting point for development. However, my concern was that because of the fact that the Deauville is a sedate touring machine (rudely called ‘Dullsville’ by some) that the standard set up wouldn’t deliver the goods for my fire-breathing monster engine with its hot cams and the rest.

                  I know that other members (Luis; frinesi2) have opted to use the various programmable control units on the market and expected to have eventually try that but know that my knowledge of electronics is meagre. So it seems that this Jetprime unit may be a very helpful thing, as it claims to be plug and play?

                  E6DADA56-B18B-4FD8-B5E4-7FC9EBA2D2A7.jpg
                  Attached Files

                  Comment


                  • #10
                    Nice project. I like your so much...
                    There are still 2 XRV750 engines running with FI one with microsqirt ecu and another with ignitech ignijet ecu. Ignitech works with the stock XRV crank sensor and uses the intake pressure sensor for sync and for the microsquirt they made a new trigger wheel welded to the flywheel because more tooth was required for crank signal an he uses a hall sensor for cam signal. Our greatest proble

                    Comment


                    • #11
                      Only a few small things done on this project recently - cleaned up some second hand NT700V pipes and pruned the frame of the - for me - superfluous frame rail that the bottom of the stock radiator attaches to.

                      However, I'm awaiting the materials (timber) for my new workshop so that should be underway soon.

                      I'm wondering if any passing electrical genius can advise me on ignition coils? The standard NT700V item has a primary resistance of 2.58 Ohms - would a coil of 3 Ohms be satisfactory?

                      I would have liked a couple of the very compact units used on the Africa Twin but they have a much lower resistance. So I've been looking for a compact compatible coil - the Dynatec mini 3 Ohm coil seems a possibility although expensive.

                      Also, the NT700V has only a single plug per head - why can't I can't use a single coil with two leads, as on a Harley or other twin?

                      Comment


                      • #12
                        We do love a good old build thread. Especialy all out crazy ones going untravled places.
                        Don't spend money and buy, spend time and learn.

                        Comment

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