Magneto drive gear

[Stu]

Hi guys. My mum isn't coming to Zambia for another month and I can't wait that long to seal up the engine of my A10.
As I've said in other posts I installed a vape electronic ignition and now must get the drive gear. My question is,I have seen, being advertised, drive gears for manual advance. Is this the gear I need to order? Fibre or alloy? Which will fit the vape ignition kit?
I know some of you get bored with the old questions but I've looked thru the site and couldn't find the answers I needed.
Thanks in advance.

[muskrat]

G'day Stu.
The manual type. I have the alloy gears on both of mine but the fiber one will do.
Cheers

[CheeserBeezer]

The reason BSA fitted a fibre gear is because it is a 'sacrificial' component. They are made of Tufnol and will strip if the magneto seizes (which they can if the armature flies apart). Using an alloy gear adds the risk of damaging the crankcase half if anything goes catastrophically wrong with the mag. The fibre gears last for a surprisingly long time and a new one will probably outlive us all. My other concern about alloy gears is that they are 'aftermarket' so I'm not sure how well the teeth mate so I'm always a bit concerned about the possibility of creating aluminium soup. I know you have electronic ignition but I would still apply the same reasoning.

[Stu]

Thanks guys

[Stu]

One last thing, sounding like colombo here.
Do I need anything else to attach the drive wheel?
The auto mech has the nut built in, might sound silly but is a standard nut gonna be ok to hold it? The hole in the centre looks quite large, but enough that even a washer won't hold it

[groily]

The reason BSA fitted a fibre gear is because it is a 'sacrificial' component.  . . . .  My other concern about alloy gears is that they are 'aftermarket' so I'm not sure how well the teeth mate so I'm always a bit concerned about the possibility of creating aluminium soup. I know you have electronic ignition but I would still apply the same reasoning.

Pretty much agree, and the sacrificial point is obviously valid - but many other marques did use steel pinions or sprockets and chains.

With the Vape thing Stu, a correct plain gear should go on OK with a plain nut and washer as the replacement bit replicates the magneto drive end - but I've not seen one in the flesh. The gear should be snug on its taper and the hole diameter on the outer end should be the same size as the bit of shaft it sits on, with the gear nicely aligned with the adjacent one?

[terryg]

Completely agree about the quality of alloy mag pinions. I have one - in a box where it’s been for years, for precisely the reason Andrew stated.

[groily]

Completely agree about the quality of alloy mag pinions. I have one - in a box where it’s been for years, for precisely the reason Andrew stated.

I did run with one, which I had modded to accept an ATD, for quite a few miles on my A10. It came from SRM iirc and the mesh and diametral pitch seemed OK from what I could see (not definitive of course). Probably did about 10K miles with it before swapping back to a new tufnol gear. No 'aluminium soup' but I thought the fibre one ran more quietly. 
A friend cut himself a gear for his sprung-hub 5T Triumph and mounted a BTH 'clock-spring' ATD on that, and it's been OK too.
I don't think they are all necessarily awful, but some almost certainly aren't great because accurate gear cutting isn't a trivial pursuit.

[muskrat]

G'day Fellas.
My plunger has had her alloy gear since the late 90's and it was a had me down from the racer when it retired. Not a single problem. The Cafe (retired racer) got a new one when she was re-commissioned about 12 years ago also with no problems.
I can't remember where I bought them. I think it was Kirby Rowbotham mag replacement Boyer kit.
I agree their a bit noisy compared to the fire gears, but barely noticeable over the alloy head/rockers racket
Cheers

[Stu]

Thanks guys, let me try one