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Faulty G83 R.H. Kickstart shaft

Seán Ó Maoildeirg

Forum Website User
Non-VOC Member
I recently fitted a new G83 kickstart shaft because the original one was twisted and slightly bent and was only discovered when I was replacing the G47 and G46AS kickstart ratchet and pinion. I retained my G82 quadrant as it was in perfect condition.
I refitted the cover having fitted the new parts from the Vincent Spares Company and a few days later decided to give the bike a run. I turned it over a few times on the decompresser and then readied it for a good swing. BANG! the kickstart went with a sickening crunch. I quickly ripped off the cover to find the Quadrant in two parts, having broken at the internal splines. Closer inspection showed the G83 shaft splines were crumbling.

I still had the original shaft and brought both shafts to get a hardness test done as the old one resisted marking with a file and the new one was like butter to the file test.
The old one measures 22.5 HR"C" and 67.5 HR"A". in other words it had a very good hardcase.
The new one measures 27 HR"C" and 34 HR"A". In other words it's hardcase was just a joke.

Do any of you metallurgists have a more suitable steel and heat treatment in mind for this job.
I have been told that the supplier is using Material – EN24W (817M40) Heat treat to ‘W’ condition 1080-1240 N/mm[SUP]2[/SUP] (70-80 Tons/in[SUP]2[/SUP])
 
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Seán Ó Maoildeirg

Forum Website User
Non-VOC Member
I'm already talking to Ian Savage about this.
Ian is talking to his supplier about it also.
But I'm concerned that any replacement kickstarter shaft will have the same material and not be case hardened correctly.
 

Vincent Brake

Well Known and Active Forum Website User
VOC Member
I have had it to and later (new one) anneald the quadrant spline a bit and ready it was, (and heated up the old one and welded it on the shaft, and remachined the short part)
 

Seán Ó Maoildeirg

Forum Website User
Non-VOC Member
I have had it to and later (new one) anneald the quadrant spline a bit and ready it was, (and heated up the old one and welded it on the shaft, and remachined the short part)

I would have liked to have done the same here but the shaft splines are too badly damaged. Don't forget that my, previously perfect, quadrant is now also scrap
 

Big Sid

Guest
On those splines , be sure your kick start arm is not butting together it's clamping ends so can't fully close together on the shaft . Very common . Use a Dremel with cutting disc to remove excess metal allowing the joint to come closer together . Sid .
 

Seán Ó Maoildeirg

Forum Website User
Non-VOC Member
On those splines , be sure your kick start arm is not butting together it's clamping ends so can't fully close together on the shaft . Very common . Use a Dremel with cutting disc to remove excess metal allowing the joint to come closer together . Sid .
I should have made it clear that the damaged splines and the ones locating on the Quadrant. The kickstart end of the shaft (Serrated) is also soft but was not YET damaged.
 
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The VOC Spares Company Limited

Well Known and Active Forum Website User
VOC Member
I was discussing this issue with Seán, but now he has to put subject on the Public Forum I will have to respond here.
The G83 shaft has been drawn with full material specification by the VOC Technical Committee, while Seán was adding this post I was driving to the manufacturer who has been making these for us for several years, to check that the drawing was followed and see the material certificate. I can confirm the shaft was made in accordance with the drawing and from the correct specified material.

Now to the problem, I have not seen the parts, only a photo and Seán’s description. Seán has made the classic error in confusing hardness with strength, the shaft Seán replaced (I won’t say ‘original’ as we don’t know the origin of this shaft) in Seán’s own words was ‘bent’ and ‘twisted’ so not very strong then.
That shaft may have been case hardened, but as we know this is a treatment to prevent suface wear and as the kickstart shaft is not rotating much or often, this is a secondary consideration. I don’t believe that if, as Seán claims, the splines on the shaft failed case hardening would have prevented it. The main consideration must be strength as we don’t want shafts that bends and twists do we? Furthermore we must not make the shaft too hard as with the twisting action and the numerous stress raising points the shaft could snap. Hence the chosen selection of the material.

As we only supplied Seán with the shaft he needed to fit it, now Seán told me he used a hammer, all be it a rubber one, to fit the new shaft and I sure he was very careful but can we be sure that the shaft was perpendicular to the quadrant at all times, could the shaft have canted over or broached and cracked the quadrant?
I know this can happen as I have assembled over a dozen G83AS quadrant assemblies over the last couple of years and even putting the shaft using a press I have cracked a quadrant.

All of that said I am of a mind to replace these parts, without prejudice as one has to say these days, in the interest of good customer service and as it could be impossible to find the initial cause when the parts are so damaged we could spend a lot of time going round in circles and Seán wants to ride his Vin and I have plenty to as well.

Note to Sid, we have an undercut in the area you describe so not problem there.

Ian Savage
VOC Spares Co
 

Seán Ó Maoildeirg

Forum Website User
Non-VOC Member
Hi Ian,

I wasn’t aware that there would be a problem with asking on the forum for suggestions on a better material and heat treatment. If doing so has caused a problem or any embarrassment to the spares company or your self I can, in all honesty, say it was not intended to do so.
I welcome your gesture in offering to replace the full kickstart shaft assembly G83AS. I stated that I was not an expert in the metallurgy field. As regards correctly aligning the shaft before introducing it to the rubber mallet, I can assure you it was correctly aligned and very easily pushed home. (I am retired after a 44 year toolmaking and precision engineering career).
The old shaft may not be an original but the difference, in the case hardening is startling to say the least, to the new one, from the Vincent Spares Company.
If you would like, I can return the damaged G82 shaft when I have received the replacement items.

I would like to ask you to please do a file test on the replacement parts to establish that they have been case hardened before dispatch

Yours truly,
Seán
 
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