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  • Griffon Enduros

    Our "Bibles" tell us that there were both 250 and 380 Griffon Enduros which greatly resembled the Scramble bikes except for a few minor details. Obviously there was a bigger tank, a thicker seat and lights and different gear ratios, but what about the fundamental question of engine tune? The specs I have seen have a lower BHP rating for each size with a reduced compression rating. So how was that done? Did they put a compression plate under the barrel, under the head, or by other means??? AND.....what system was used for ignition and lighting?

  • #2
    Griffon Enduros

    The CR would have been reduced by a decompression plate twixt head and barrel. Putting one under the barrel cocks up the port timing.

    For lighting Greeves would use the larger Motoplat unit with lighting facility. The larger flywheel wasn't a problem on the 380 (it had a larger flywheel) but could prove a bit restrictive on the 250.

    A few chaps use a large Motoplat unit on their pre74mx bikes. Not for an advantage but purely because that's what their bikes came with.

    Druid

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    • #3
      Druid, thanks for confirming my own thoughts. What can be used on a pre-72 bike that presumably used a Steffa generator and points set-up?

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      • #4
        Griffon Enduros

        The ISDT Challengers used a special Steffa K1 mag with a modified mainshaft. I believe that Electrex World can make a Steffa repacement with a lighting facility. The last ISDT Challengers had 2 windings on the LT side to give a few watts for lighting.

        Druid

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        • #5
          Motoplat lighting facility

          They say ignorance is bliss and I'm afraid I am blissful on motorcycle lighting. My Griffon has no function to add lighting, but having read that a Motoplat can have a lighting function, how does this work? is it minimal power, or am I totally in cloud cuckoo land?Please be kind in your replies. Anything to do with classic cars-no problem!!!......................starider

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          • #6
            Motoplat lighting

            The Motoplat lighting version is a different animal to the MX unit. It's larger which means it has a different back plate and cover but it fits on the std mainshaft.

            If you'd like to fit one try Kenny Sykes in the US, they took a few models with lighting.

            Druid

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            • #7
              Thanks Druid! We may need to talk to Electrex World then!

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              • #8
                You could modify a flywheel mag from a jap bike (Yamaha DT175). Need a bit of machining though both on flywheel (taper) and back plate, but possible & cheap (can be picked up on eBay for around £50 or from a bike breaker) if you have a lathe and the skill to use it.

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                • #9
                  At present this is a feasibility study to see what is available. Lathe and skill is available to me but not for the next few months as we are changing the workshop.

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                  • #10
                    Originally posted by Brian Catt View Post
                    At present this is a feasibility study to see what is available. Lathe and skill is available to me but not for the next few months as we are changing the workshop.
                    Hi Brian, I have a 250 and a 380 Griffon on their stands ready and waiting for the conversion to start. It will be brilliant to take part in a few enduros never mind the odd Sunday ride.

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                    • #11
                      Brian
                      This guy used a new pit bike 12volt flywheel mag on a Yamaha T80 (see https://www.youtube.com/watch?v=EOltaIo4Bk8 )
                      He put all the pics up at the time on the Townmate Forum but they have been taken down by now. If you contact him via Youtube he will give you the details.
                      I think the whole mag unit only cost around £65 new.

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                      • #12
                        OK Craig, we will need to chat over what I have been finding. My initial thought is that we need to aim for the Pre-72 class where it seems the opposition, at least in this year's ISDE, was fairly low. The Enduro models were down tuned it seems by putting a decompression plate under the head. I have done some calculations and it would appear that 1.5 mm for the 360 and 1.0 mm for the 250 would give about the stated compression ratio.
                        We have talked about the gearing and we will need to sort the Medium wide gears as the standard MX gearing is too close. My only fear is that the 250 will still be too peaky to pull the intermediate box, but that will be trial and error!

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