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Griffon 380....or 360....or QUB

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  • #16
    Originally posted by dave higgins
    Soggy, apart from the jetting itself & the throttle slide, the main difference is the main jet spray tube, the two stroke having a 45 degree ( ish ) champer to it & the four stroke being a flat top.......
    Which leads neatly to the next question Dave, why do a 2 stroke and 4 stroke engine need such a different carb? Perhaps I am over thinking this....

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    • #17
      I'd hazard a guess that it's something to do with the atomisation of fuel plus oil. Perhaps we have an expert in laminar flow who may give us the story.....

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      • #18
        Additional Info

        Paul - To be clear - there are 3 main differences between a 2 stroke and 4 stroke Amal carb

        The shamfered spray tube as mentioned above
        The Needlle jet is different, a 4 stroke has the jet at the bottom threaded end and has a bleed hole, the 2-stroke needle jet ahs the jet at the top o fthe body and no bleed hole
        The main jet holder - is longer on a 4 stroke as the main jet sits lower in the float bowl.......

        All aimed at getting the mixture richness correct to suit the type of engine characteristics.........

        see attached article and go to pictures on page 9

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        • #19
          Thanks Kim, an excellent reference document and answers my questions and then some! I guess we all take our carbs for granted and don't consider what an amazing piece of precision engineering it really is. Back to the workbench for me then....

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          • #20
            Brilliant article Kim! Why did I waste all that time working out the 626 for myself and putting in all in Leading Link?!

            The information age, eh what?

            ....and these people who say they don't do computers!

            It's like grading a track with a garden rake when you've got a tractor you refuse to use!

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            • #21
              My Silverstone has a 36mm Mk2 Amal fitted, and when I had stripped and cleaned it I noticed the pilot jet was in the float bowl, supposed place for a 4 stroke, so I put it in the body, again supposed best place for a 2 stroke. Started OK but wouldn't rev cleanly when I went out on the track. Returning to original position and all was well. Amal leaflet actually says" This is not a hard and fast rule and the reverse may sometimes be the case" Dogsbody

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              • #22
                steering head bearings

                Hi all,

                Anyone know what size taper roller bearings I need for the griffon. I've picked up the ceriani forks and yolks to replace the none standard ones that came with the bike, so size should be to original factory spec. I've seen elsewhere on the forum good things said about Timkens from QualitybearingsOnline, so if anyone can help with internal and external dimensions, it's just one click and job done.

                On the subject of forks, anyone have a preference / good experience of hard chroming companies?

                In other news, gearbox just dispatched to Geoff Nunn for some tlc. Kim, when the box returns I'll let you know how many gears should be in there.

                Paul

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                • #23
                  Good progress Paul !! Ref years it's not the number in there that is the issue I know there are 4 ... It's more my inability to se more than n fixed gear per race 😂😂😂😂

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                  • #24
                    Originally posted by Soggy Welly View Post
                    Hi all,

                    Anyone know what size taper roller bearings I need for the griffon. I've picked up the ceriani forks and yolks to replace the none standard ones that came with the bike, so size should be to original factory spec. I've seen elsewhere on the forum good things said about Timkens from QualitybearingsOnline, so if anyone can help with internal and external dimensions, it's just one click and job done.

                    On the subject of forks, anyone have a preference / good experience of hard chroming companies?

                    In other news, gearbox just dispatched to Geoff Nunn for some tlc. Kim, when the box returns I'll let you know how many gears should be in there.

                    Paul
                    Hi Soggy,
                    Check out my QUB Mk2 post. I used a company for the front forks that where quick and very good

                    Comment


                    • #25
                      Acknowledged experts for chroming forks are Philpots in Luton (www.pittedforks.co.uk). There may be others nearer, for example Precision hard Chrome in Doncaster, 01302 330050.

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                      • #26
                        Dynasurf for fork rechroming

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                        • #27
                          Thanks chaps,

                          I'm aware of the good reputation and years in the business of AM Philpots - I was looking at having them replate the stanchions on my 1976 Honda 750/4 also. but at 175.00 it seems a bit steep. I could buy a new set for less money. though of course the same argument doesn't apply to the cerianis.

                          any thoughts on bearing size?

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                          • #28
                            gearbox woes (continued)

                            So the gearbox that came with the bike has been condemned by Geoff Nunn as not economically viable to repair. bent shafts, worn gears, cracked case....the list is long.

                            however, a complete gearbox has materialised which was rebuilt by Geoff some 4 years ago and never been run. unfortunately my clutch is the 5 spline version and the new box is 6 spline. I have a replacement 6 spline bottom plate but am a bit unsure how to remove the small circlips from the spring pegs to dismantle the cutch. I'm assuming I need to squeeze the whole thing up in a vice to compress the springs so the circlips will come clear of the recesses in the top pressure plate. Any tips appreciated.....before I go in heavy handed and damage something.

                            Paul

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                            • #29
                              Fiddley Job

                              Hi Paul..

                              Glad you are making progress..

                              My uncle made a tool that screws into the posts.. You can then compress the spring a take the clip out..

                              It's worth making something up.. I will take some pics when I get a chance of said tool..

                              Griffon clutches are a pain to work on..

                              Regards

                              Scott 151

                              Comment


                              • #30
                                That would be a great help Scott.

                                Meant to say hello at Marks Tay on Sunday but managed to miss you. Saw you on the track though, looking pretty smooth it must be said

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