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Dommy slider threads

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looking through the tech books and our suppliers  offers there is some confusion as to the threads of the bridge studs , they are either  cycle or BSF.    logic would say whitworth into the slider and cycle for the nuts ,  But no .  cycle I think. RGM  say BSF.

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The DSNs quote the fork mudguards studs as 1/4" BSF.  Part number  067523.  These being 26 tpi which matches the CEI equivalent size thread.

The later Commando variant of this stud had a 1/4" BSW x 20tpi thread which like many Whitworth threads morphed into a 1/4" x 20 UNC thread. Part number 0633189

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Hi Phil, I did see that in the DSNs  but had not realised that 1/4 bsf and CEI  were compatible ,  All i have to do now is get the broken off studs out .   Was going to drill out but now favour welding nuts onto the stud remains. Can try that when welding new feet onto the SS and 99  centerstands. . Also need to equalise the fork lengths , had to do this to all my Nortons ,helps to reduce the struggle to fit wheel, axles then  just slide home as if they are keen to  get back together!. No mallets needed.

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I did that once, had a worn out steel stud (about 3/8 dia) in a Reliant ally crank block. Rough welded a nut on, BINGO the heat from the welding allowed the stud to just unwind, back in business! Let us know how you get on? Drill out a steel stud in ally, very dodgy. AND as for those 'easy outs' nice idea that does not work.

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I have drilled out a 3/8" stud in the case and the residual stud remains just "peeled" out ,no problem.  I suspect it was just a fluke though and helped by the bigger size. welding seems safer as i have a bit of stud to weld to. I wont be doing it as Pacemaker fitted. I instructed son that he HAD to learn to weld and MADE him practise ! . A good investment dont you think?. I also ensured he bought a house with a big garage to slip the odd bike into .   Crafty huh ?.

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The nuts welded onto the remains of the slider studs got them out ,but there was a lot of waggling back and forth. The new studs from RGM were a bit odd with a plain shank in the middle and threads too short to properly engage in the slider threads . The plain shank was also too long and would have left the mudguard loose . A session with a 1/4 cycle die got them sorted out. A lot a faffing around with damper rod nuts eventually got the sliders the same length and now the axle will pass through both legs with a finger pressure . No need to carry a hammer in the toolkit !.The fork oil was strange, 1 leg with clean ATF in it ,the other with grey sludge . That will have to do as I don't intend to ride the SS much .  I hear that they are the most unreliable of the Twins, but why should that be ?.   Made in Plumstead ?    OOH  , thats going to ruffle a few feathers !.

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Yes Bob - You're probably right.  The early Bracebridge St 650es did suffer reliability issues but they were definitely the fastest of the breed.  Too much power for the flimsy con-rods that they fitted.  The Plumstead ones were more reliable because they were heavier, but slower.  They seemed to give up on them once they had decided to race the G12 CSRs and with the Unified Twin and the Commando already on the drawing boards.  All the foibles were sorted by the time the Mercury was built so what did they do ? - Stick a silly price tag on it, remove a carb and sell them to Police Forces around the world.  They could not have a 650 out-performing a Commando could they ??  That's the Matchless mentality for you.  On that happy note I wish all you readers a Very Happy New Year for 2024.  Cheers to you all, Howard

 


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