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  • Eight valve DOHC engine

    Who made the first motorcycle 8 valve twin cylinder DOHC engine and when ?

    No prizes but I think you will have a suprise.

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    Last edited by John Stevenson; 07-26-2008, 11:16 AM. Reason: Added twin cylinder to the text.
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    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.




  • #2
    Easy, the Honda NR750. They made room for eight valves by using some oddball oval pistons, with two rods each. It was basically a V-8 with each pair of cylinders siamesed.

    As I recall that was back in the early eighties. I don't remember the specifics, or how well it did in the races (it was a pure race bike) but I know they released a very limited number of street versions, which sold for some truly absurd amount of money- like $100K or more.

    Gorgeous bike, I'd have loved to have one, but it's one of those things you really shouldn't ride even if you can afford it.

    Doc.
    Doc's Machine. (Probably not what you expect.)

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    • #3
      It must be the Hurley Pugh

      http://www.hurley-pugh.co.uk

      For anyone close to prewar British bikes that site is worth reading

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      • #4
        Is it Vincent?

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        • #5
          Easy, the Honda NR750. They made room for eight valves by using some oddball oval pistons, with two rods each. It was basically a V-8 with each pair of cylinders siamesed.
          Hardly. Honda made a DOHC 4 valve per cylinder twin racer in 1959, the Honda 125cc Twin, took 6th at the Isle of Man TT.

          The one I want is the Honda 50cc Factory Racer. It was legendary in the 60s as it could do 100 mph. I could ride that here without license or insurance as it is only 50cc and falls in the "limited speed motorcycle" category. All the regulations here are based on displacement, not horsepower. The 50 racer was a twin and revved to around 20,000 rpm.
          Free software for calculating bolt circles and similar: Click Here

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          • #6
            Originally posted by Evan

            The one I want is the Honda 50cc Factory Racer. It was legendary in the 60s as it could do 100 mph. I could ride that here without license or insurance as it is only 50cc and falls in the "limited speed motorcycle" category. All the regulations here are based on displacement, not horsepower. The 50 racer was a twin and revved to around 20,000 rpm.
            23,000 actually Evan.
            Had one here once, at least the crank out of one to press it apart for a new big end bearing, my press wouldn't take it so took it round to ZF Gears to use their big press.
            Got it to 87 tonnes and bottled out, too much was creaking and groaning, gave it back to the guy as it was.

            These early racers are very rare, there are a few Honda's about but Suzuki and Yamaha used to take theirs about 5 miles offshore and dump them in the pacific so no one could have access to them.

            Somewhere I have pictures of one of the 350 Honda twins that managed to 'escape' but they smashed every fin off the barrels and broke every casting.
            I spent hours making and welding new fins on.
            It probably would have been cheaper to have new cast but the guy wanted it 'original'.

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            PS Nice one Charles,not seen that site for a while.

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            Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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            • #7
              My first bike was a Honda 50. I spent many hours tuning and fiddling with it. A friend of mine had a very early prototype Honda 305 Superhawk, all tube frame. It would burn rubber for half a city block except every time he pulled that trick he had to replace the chain tension adjusters on the rear axle as they ended up bent in a U shape.
              Free software for calculating bolt circles and similar: Click Here

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              • #8
                harley in the 20's i think it was a boardtrack bike.

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                • #9
                  Is that eight valves per engine or cylinder?

                  If it's per cylinder I'd go with the Honda NR750.

                  I heard a rumor that their process for boring the oval cylinder is still a secret.

                  Harley did build an eight valve v-twin in the twenties. It was very fast. It could do over 120 on the mile dirt tracks. Braking was done with a compression release. It was an OHV however. And not the first.

                  Forgot to mention that they were still using clincher tires on that Harley.
                  Last edited by topct; 07-26-2008, 09:56 AM.
                  Gene

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                  • #10
                    Originally posted by topct
                    Is that eight valves per engine or cylinder?
                    Ooops should have included the word twin in the title, so we are looking at 4 valves per cylinder.
                    Doc got a right answer, don't know if it was the first or not but it wasn't the one I was looking for.

                    .
                    Last edited by John Stevenson; 07-26-2008, 11:16 AM.
                    .

                    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                    • #11
                      Gordon Brown our prime minister said the Indian's are making a car brand new on the road for a thousand pounds don't know anything about it but talk about global warming they reckon a million will be sold in India alone.Alistair
                      Please excuse my typing as I have a form of parkinsons disease

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                      • #12
                        Sorry Alistair it wasn't Gordon Brown.

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                        Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                        • #13
                          1983, Triumph

                          "TSS-engined T58-1 with rubber-mounted, eight-valve engine aimed at police use is designed. The TR6 is reduced to 600cc. A prototype water-cooled, 900cc bike called the Phoenix (the engine was also known as the 'Diana') is designed in early 1983 (a water-cooled, twin OHC vertical twin)."
                          Gene

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                          • #14
                            Originally posted by John Stevenson
                            Ooops should have included the word twin in the title, so we are looking at 4 valves per cylinder.
                            Doc got a right answer, don't know if it was the first or not but it wasn't the one I was looking for.
                            -Ah, see, you didn't say that.

                            To me, when somebody says "four valve" or "five valve", it's assumed you're referring to "per cylinder". That's why I thought the question was suspiciously easy, since Honda's oval setup is pretty much the only way you're going to get room for eight valves per bore.

                            Hardly. Honda made a DOHC 4 valve per cylinder twin racer in 1959, the Honda 125cc Twin, took 6th at the Isle of Man TT.
                            -Hardly what? The NR had eight valves per cylinder, which is what I thought John was asking. Eight valves total, for an unspecified-at-the-time twin? I couldn't say, but you're right, it was way earlier than the NR.

                            Doc.
                            Doc's Machine. (Probably not what you expect.)

                            Comment


                            • #15
                              Peugot in the early 1900s?

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