Author Topic: striped magneto gear  (Read 369 times)

Offline kiwi george

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striped magneto gear
« on: 27.07. 2015 08:35 »
My 54 a10 stopped on me on a club run on Saturday with an enormous backfire, the timing was checked & found to be well out diagnosis was a stripped fiber gear. This appeared to be caused a worn drive side bearing in the mag however on close examination of the gear it was found that the meshing with idler gear was only about 2/3rds of the full width of the fiber gear. my question is what controls the depth of the meshing? as it is locked on the taper on armature shaft. The premature wear on the bearing is a puzzle too as its only done about 9000 miles, the earth brush is okay.
Can anyone  suggest a fix please?

Online KiwiGF

  • Last had an A10 in 1976, in 2011 it was time for my 2nd one. It was the project from HELL (but I learned a lot....)
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Re: striped magneto gear
« Reply #1 on: 27.07. 2015 08:48 »
Do you have the auto advance retard unit? I ask as if not an ally gear would probably be stronger. Than a fibre one......but as far as I know these ally gears are only available in solid form for manual advance mags (or in my case for my BTH electronic mag).

I suspect there are a lot of bikes with gears that do not engage the full width, mine don't!

New Zealand

1956 A10 Golden Flash EA7-168x, CA10 913x, left BSA together for Liverpool, 5th Dec 1955.

1949 B31 rigid “400cc hot rod” (favourite bike)

1949 C11 rigid, but why!!! (cos it was cheap)

1937 B21, missing parts so mission impossible?

1952 Armstrong Siddeley Whitley for rainy days (with wife).

GL1800 Goldwing not sure why, maybe cos it always starts

Online chaterlea25

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Re: striped magneto gear
« Reply #2 on: 27.07. 2015 11:32 »
HI George,
If the mag bearings were worn or the paper insulating washer around the bearing has broken up them the mag armature will be forced away from the idler gear by the taper on the drive gear teeth

Alloy gears for the ATD are available,
Try Beezermac (Priory magnetos) here on the forum or Tony Cooper

1961 Super Rocket
1963 RGS (ongoing)