Author Topic: A7 52 star twin  (Read 477 times)

Offline KeithA

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A7 52 star twin
« on: 14.11. 2015 11:41 »
Hoping some of the experts can help me?
How is the dynamo sprocket removed??
I have undone the nut. Tried with a good quality puller against the back of the teeth. Done it up fairly tight. then applied some heat directed to the main body of the sprocket.
It jumped on the shaft a bit, and the puller went loose.
I tried 20 minutes later, again applying some heat, but now it just wont budge.
I 'm at the point where I think I am doing some damage, either flaring the end of the shaft, or altering the temper of the sprocket from the heat.
Any advise is appreciated.
Thanks in advance.
Keith A


Offline beezermacc

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Re: A7 52 star twin
« Reply #1 on: 14.11. 2015 16:22 »
I normally remove the dynamo completely with sprocket attached and then pull the sprocket off with a bearing splitter.
Priory Magnetos Ltd - A10 spares, magneto and dynamo refurbs. www.priorymagnetos.co.uk

Offline KeithA

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Re: A7 52 star twin
« Reply #2 on: 14.11. 2015 18:24 »
Yes I have the dynamo removed from the engine.
Keith

Online bsa-bill

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Re: A7 52 star twin
« Reply #3 on: 14.11. 2015 18:35 »
Quote
Done it up fairly tight. then applied some heat directed to the main body of the sprocket.

Don't know if you gave it a tap, you don't say, but generally put tension on the puller then give the end of the puller screw/thread a sharp tap, should spring off.
Certainly I'd do this before applying heat
All the best - Bill
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1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline muskrat

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Re: A7 52 star twin
« Reply #4 on: 14.11. 2015 19:32 »
G'day Keith.
The shaft and sprocket are a tapper fit so once it cracks it should fall off. I'd say the puller slipped a bit.
The bearing splitter beezermacc mentions are the best type of puller to use.
http://www.crazysales.com.au/online-12pc-bearing-puller-and-separator-tool-61793.html?utm_campaign=Hand+Tools&utm_term=FS7010&utm_source=source&utm_medium=medium&aid=11&gclid=CK2A5sPTkMkCFdckvQodNLAMOw
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Online trevinoz

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Re: A7 52 star twin
« Reply #5 on: 14.11. 2015 21:31 »
Don't pull on the teeth.
Mostly I can get them off by wedging two screwdrivers, one each side, and levering up. Keep the nut a couple of thread engaged to stop the sprocket flying off.
When this fails I use the bearing splitter but I have made a blind nut with a centre in the end which I screw onto the shaft to protect the end of the armature.

Offline beezermacc

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Re: A7 52 star twin
« Reply #6 on: 14.11. 2015 23:37 »
Trev is right, don't pull on the teeth, use a bearing splitter under the body of the sprocket. I use an aluminium blank between the shaft and the splitter to prevent damage to the armature.
Priory Magnetos Ltd - A10 spares, magneto and dynamo refurbs. www.priorymagnetos.co.uk

Offline KeithA

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Re: A7 52 star twin
« Reply #7 on: 15.11. 2015 02:39 »
Thanks for all the advise. Much appreciated.
I will have to obtain a bearing splitter, and consider protecting the end of the armature shaft better.
The puller I was using is a good quality solid 2 leg type, that grips and contacts under the teeth, but close to the body of the sprocket.
It sits nice direct on the end of the shaft, as well, but it is starting to mushroom when I tried a good knock to the end of the puller with a copper hammer.
This really is a tight taper fit sprocket. No doubt!!
I will have to turn up a mandrel, with internal thread and blind hole, to support as much of the exposed threaded end as possible, and use an aluminium blank, as suggested.
I'll let you know how I get on.
Cheers Keith

Offline TT John

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Re: A7 52 star twin
« Reply #8 on: 15.11. 2015 20:21 »
Keith. When you do get it off replace it with a belt drive kit from Dynamo regulators ltd, you get the whole kit which includes new sprockets and new nut for the dynamo, I have replaced the chain drives with this product on both my A7 & A10, gives better charging at lower revs also.

TTJohn