Kick start Quadrant shaft

[John Cone]

Can any of our learned people tell me what the exact diameter of the quadrant shaft should be? I know the new ones are longer but there seems to be a conciderable difference between the old and new in diameter.

 

[Tom Gaynor]

I'd like to think I was learned, make an effort to learn stuff, but point out that being learned is a condition that IME is swiftly overtaken by age-induced inability to remember what one has learned. So I may well have mic'ed up the kickstart shafts, must have done since I junked the oilite bush, of a thin-ness that Durex might envy, in favour of a stainless one. But the actual numbers? Forget it. I certainly have.
I'll have a look tomorrow. I think it's 3/4". What I do remember is that my kickstart lever fitted the new shaft in exactly the same way as it had fitted the old factory original, so at least the spline's effective diameter hadn't changed much.
But since |I was following Francois Grosset's advice in fitting the longer shaft, you don't have to live in 221b Baker Street to figure out why the stainless bush has given no trouble.
Why a 1/4" longer shaft is what the factory should have made standard in the first place, giving 1/8" clearance from MY exhaust, need not concern us here.

 

[A_HRD]

Can any of our learned people tell me what the exact diameter of the quadrant shaft should be? I know the new ones are longer but there seems to be a conciderable difference between the old and new in diameter.

John,

Assuming you're talking Twin here, I think you'll find it should be a thou or two down on 0.700 ins. I don't have one to hand to measure, but I do have a sketch I made of the G86 spacer and I made that to suit a new shaft, a couple of years ago, with an ID of 0.700.

Peter B
Bristol, UK

 

[Tom Gaynor]

So much for memory. Not very accurately measured, because lack of access means using a very near caliper, it's 0.703", 17.85 mm.

 

[clevtrev]

John,

Assuming you're talking Twin here, I think you'll find it should be a thou or two down on 0.700 ins. I don't have one to hand to measure, but I do have a sketch I made of the G86 spacer and I made that to suit a new shaft, a couple of years ago, with an ID of 0.700.

Peter B
Bristol, UK

A Comet is the same.

 

[John Cone]

Thanks guys. That explains why my new shaft will not go into the inner or outer bushes. My old shaft measures 0.6875 or 11/16ths and was a slack fit but not excessive. I've had to turn down the inner part of the shaft by 2 thou ish and so not to damage the serations/splines reamed out the outer bush. Peter i will also have to turn a spacer for the outside of the cover to stop side twist on the lever. To me the measurement I have on the old shaft of 11/16 would have made it more easier to line ream using a standard size reamer on the two bushes if needed. PS/ The shaft was change because the seration end of the shaft had twisted/rung.

 

[ogrilp400]

G'day John,
Why not ream .702" straight through the two bushes and that way they will be in alignment. I have run across them out of kilter. I have two shafts here and yes they are .700". Why Vincents picked odd sizes like this is beyond me. The speedometer drive gearbox is another weird size too. The I know that there would have been an explanation but it really is perplexing. 3/4" would have been more applicable as I have sheared two K/S shafts in my time.

 

[A_HRD]

Funny Sizes

Why Vincents picked odd sizes like this is beyond me. The speedometer drive gearbox is another weird size too.

I guess Vincent just followed the standard set by Burman and Smiths respectively. It was common-place in those days to use weird shaft sizes, bearings and threads so that the world had to come back to you for spare parts and refurbishment. Alfred Herbert in Coventry (machine tool components) was another one who favoured this approach.

If you can still find a Company locally who regrinds tools, it might be worth getting him to make you a 0.702 parallel reamer from a std one - e.g 45/64ths (0.7031) or 18mm (0.7087). I don't have one either - so I might just invest in one too.

Peter B
Bristol, UK

 

[John Cone]

I agree with you Peter, i have a set of straight cut reamers, 1/2, 9/16,5/8./11/16 and 3/4. i used an adjustable reamer for the outer bush but didn't like to try line boring with it so found it easier to take it off the shaft in the lathe for the inner side. besides i didn't want the bike off the road any longer. If the return spring hadn't broken from the top hook and fallen down and behind the quandrant i proberly would of never taken it apart. it made a mountain from a molehill for me. Oh Well.

 

[Alan J]

I wrote a lot on this thread, then lost it!! I have just replaced my shaft as it too was twisting!-it appears to be 11|16" dia.-how many ways can you measure it? answers on a postcard, please! At the "Riders Rally" me old kickstarter slipped- I blame the man who has been jumping on it for 35 years! New ones are not available any where! Kind Mr. Savage has offered me alone of one if I am desperate. I am off to "la belle france" in 3 weeks time. It was most embarrassing to have to be pushed 3 times in the pouring rain to get back to Daventry on "the worlds fastest motorcycle! I might in desperation weld it all up together!-OR, buy a Kick start from Kettering for an A.M.C. burman box, cut and weld them together!