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Magneto sprocket key way?

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Just removed the magneto sprocket on my 1935Es2, after a struggle. The sprocket doesn't have a key way slot and neither does any that I have seen for sale i.e. Rgm and racing Norton, but the magneto shaft does. Any idea why this is the case? Also the shaft isn't anywhere near central in relation to the aperture in the case. I'm thinking maybe that's why the sprocket was such a pig to remove as the boss on the sprocket was stuck on the inside of the aperture in someway. I need advice please if someone can help.

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No key - mag sprocket needs to be able to be positioned about the shaft to set the timing . The taper fit is more than adequate to keep it from slipping. They are indeed difficult to remove as you discovered.

There are several threads somewhere describing tools that can be made to aid in removal.

I bought a vernier magneto drive from King Pin and I have to say it's the best thing since canned beer! Makes timing a breeze and also magneto removeal easier too. 

I'm thinking your armeture may have come from a stationary engine.  I've seen a few with keyways and I expect timing isn't that important on them.

Don Anson Melbourne 

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If the taper is in decent condition there's no need fr anything else. If not, lap it in with some fine grinding paste.

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My engine is a 1953 ES2.  This is a very small key similar to a British (and American) Standard No. 303.  (BS 46-1-1958 obsolete).  However the dimensions do not match a standard 303 key.  I was wondering if this part is available.  After a lot of work filing down a standard 303 key to fit, I was wondering if this part is available.  I can't find it on RGM Norton, etc.

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The keyway on the starter motor of my Electra was damaged. I just lapped the sprocket onto it, omitting the key, and it's held for many starts (or attempts thereat). This shows that a well fitting taper can transmit far more torque than your mag sprocket will experience.

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The magneto has a taper drive. Other wise you cannot time it correctly.

 



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