forum Forums Technical Back to Dellorto Carbs

This topic contains 11 replies, has 4 voices, and was last updated by WestEndGuzzi WestEndGuzzi 1 month, 1 week ago.

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  • #10828
    WestEndGuzzi
    WestEndGuzzi
    Moderator

      Edith is back on the road following her winter overhaul.

      I’ve refitted the Dellorto Phf36 carbs, replacing the Webber DCOE40.

      The main reason for fitting the Webber was to cure the problem of cutting out on bends etc. but I was not completely satisfied with the result.

      Now she runs as she should, thanks to advice from muselermark and others.

      The set-up. (Video here)

      Phf36 carbs on splayed out manifolds, bought new when I built the car 13,000mls ago.

      Now fitted with Anti Surge Washer PtNo.10428, fitted above the main jet holder (£4-20 ea +vat from Eurocarb) (link)

      I believe this to be the magic component that has cured the fuel starvation on corners,. Thanks Mark.

      Swill pot fitted to give gravity fuel feed to the carbs, return pipe taking pressure back to tank.

      Carb vent pipes taken up to high level under bonnet, on top of breather box.

      Exhaust balance pipe and expansion boxes removed, giving straight through pipes.

      ‘Progressive’ throttle linkage fitted, replacing the 2 into 1 cable thingey. (Video here)

      This gives a much more relaxed start and smoother town running.

      To conclude, I am thrilled with the improvement to the overall feel of the car. Well worth the effort.

      And here is a short video of the result!  

    • #10840
      david
      david
      Member

        result,,,yes impressive..seems to go really well, loved the wheels gently rollin up and down…body stays flat or so it looked…

      • #10842
        doverhay
        doverhay
        Member

          Did you find any difference running the engine without the exhaust balance pipe? It certainly looked ok based on the video.

        • #10843
          WestEndGuzzi
          WestEndGuzzi
          Moderator

            Yes.
            I think it is a definite improvement. She even sounds like a Vee twin now!

            You can get a 500 single tuned perfect, so why not 2 x 500s?
            The cross pulse in the pipes would be early into one pipe and late into the other, Interfering with the smooth running of each pot.
            I cannot see the logic for it being there, especially with twin carbs.
            It’s possible that with a single carb there may be a beneficial effect,
            A lot of the Pembly guys have a link pipe on small & large block Guzzis and the 602 2CV engine.
            But why? Can someone explain?
            I don’t recall Guzzis ever being run on a single carb, they have a link pipe/box so why is it there? Additional silencing perhaps.
            Certainly saves a lot of expense and weight on stainless work.

            So far, my trial has been a sheer delight, how much is result of reverting back to the Phf’s, gravity swill put, progressive throttle, exhaust pipe……… I don’t know.

            The bends were done by slitting with 1mm disk nearly through and then tig welding back together.

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          • #10845
            billdavies
            billdavies
            Member

              Hi Tony,
              Nice pipe work with complex bends. Folk do not appreciate the work involved and the disasters that occur.
              My Trike is running on two carbs and other than the fuelling problems of last year it runs well and the engine appears to be in balance.
              Your complex two to one cable set up is complex but looks good and appears to work well…but can you repair at the roadside if a cable breaks…I just used a simple bike part and carry standard cables as spares.
              Hope to see you on some of the outings this year
              Cousin bill

            • #10846
              WestEndGuzzi
              WestEndGuzzi
              Moderator

                Thank you Cousin Bill.
                Good to hear that your motor transplant has turned out successful.
                The layout for the cables gives them all nice easy sweeps with no kinks and no pulling at an angle where exiting adjusters etc. Hence the fulcrum. I was inspired by the very complicated linkages on the SU carbed Jaguar engines.
                I make my own cables and they can all be changed easily at the roadside without fuss. I carry a spare lower cable and one second cable.
                The botton cable has trumpet nipples rather than the small carb nipples, much stronger for the main pull. The second cables have the normal 3mm carb nipples both ends. I get all my cable supplies from Venhill (Web site)
                Use galvanised wire not stainless. (can’t be soldered).
                I did put some comments in a thread about soldering (here)
                Best wishes
                Tony

              • #10860
                WestEndGuzzi
                WestEndGuzzi
                Moderator

                  And another thing.
                  Changing a throttle cable with one of those 2 into 1 thingies is not easy.
                  You have to release the carb end of the cable before it will come out of the 2-1 barrel. With a strong spring in the carb and an accelerator pump actuator to contend with, it gets a bit ‘springy’.
                  So, I made the 1st end of the cable easily detachable from it’s actuator. This then gives enough free inner cable to take virtually all the tension from the throttle spring.
                  Similar principle on Daisy the Pembly, quick release of the ‘A’ end of inner cable, but without the progressive mechanism.
                  Or you could take the simple approach and have 2 cables direct from the throttle pedal……….

                • #10928
                  david
                  david
                  Member

                    I had a new -just msva’d guzzi JZR !!! a long time ago without a balance pipe and that performed really well and sounded good.. But i spent a year altering suspension and handling issues.different uprights/ built in some caster!!/guzzi brakes/machined splined hubs instead of bolt on adaptors/19″ wheels and avons..[.but then bought a mk 1 Triking which instantly handled far better…]
                    I might try removing the balance pipe..as I gather it helps extract gases from the other cylinder but as you mention,the beat is different so might interfere more than help…

                  • #11232
                    WestEndGuzzi
                    WestEndGuzzi
                    Moderator

                      Since taking off the cross pipe and 2 expansion boxes, the exhaust was much noisier.
                      So I reverted back to the original Guzzi silencers from the donor bike. That improved the exhaust note to a sensible level.
                      However, between 2500 & 3000rpm I was getting a very loud intake noise. This was at the critical cruising speeds of between 55-65mph.
                      The noise was metallic, throttle slides slapping back and forth.
                      The first thing to try to get rid of the organ pipe resonance was to put a metal slide in the inlet pipe, post carb. I tried it vertically and horizontally but that didn’t work.
                      Inlet eliminated, must be the long exhaust pipe before the silencer.
                      So I put an 18″ long home made baffle into the front of the long pipes.
                      Bingo. It works. Resonance eliminated!

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                      • #11234
                        doverhay
                        doverhay
                        Member

                          I’m confused Tony, what is the picture showing, it looks more like the inlet pipe rather than the exhaust??

                      • #11236
                        WestEndGuzzi
                        WestEndGuzzi
                        Moderator

                          Well spotted Dick!
                          That is the inlet pipe.
                          That’s the bit that didn’t work.
                          I have a couple of pictures of the baffles on my hard drive, but I can’t find them!
                          So you can either wait till I find them, or I extract similar items from Daisy’s pipes to reposition them, take new pictures and file them where I can retrieve them.
                          If you want to see the pictures, you have to loggin!

                        • #11240
                          WestEndGuzzi
                          WestEndGuzzi
                          Moderator

                            By popular demand, here is the baffle, courtesy of Daisy.
                            30mm pipe (inside the 38mm side pipe) with slots cut in it, then one side of slot bent inwards.

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