Rotor question

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mikeydpippin
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Rotor question

Post by mikeydpippin »

Just replaced rotor stator and regulator, had a gap of 2 rounds of insulation tape around the rotor when fitted.
Took it for a short ride and could smell burning, quickly returned home and as you can see with the photos very slight scuffing on the stator.
You can see slight lines on the rotor and lighter marks above the terminals
Will take rotor to engineering company tomorrow, my question is:
How many thou would you suggest taking off of the rotor.

And am I lucky to get away without seizing engine?..
Hopefully stator will work...
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Mike
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ajscomboman
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Re: Rotor question

Post by ajscomboman »

Does seem to be a problem with these rotors at the moment. Take another 4-5 thou total off the rotor and it'll still be fine. I think Big Wol took nearly 7 thou of his (that's total, so 3.5 thou skim cut) and it still worked spot on.
mikeydpippin
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Re: Rotor question

Post by mikeydpippin »

Thanks Rob, I will go for 5 thou to be on the safe side👍👍
Mike
JimFitz
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Re: Rotor question

Post by JimFitz »

Hi Mikey

You should not need to have the rotor skimmed. The normal practice is to use some brass shim over the pole pieces when fitting the stator and then pull them out after the stator has been tightened. There is normally some movement of the stator on the mounting studs so it needs to be centralised.
I am not sure what the clearance should be between the rotor and the stator pole pieces but it is pretty small - I would guess at somewhere around 10 thou.
After fitting and before running it is important to check clearance on all the stator poles by turning the engine in steps of about 45 degrees and checking clearance on the poles. Some feeler gauge sets have a brass feeler for this purpose.
I wonder if you have some play in the main bearing or maybe a little eccentricity causing wobble of the rotor.

Jim

Just read the previous two posts. Of course, if the rotors have been made too big then they would need skimming.
Too old to Rock and Roll but too young to die.

1952 G80 rigid, 1960 G12 DL / Watsonian Monza, 1954 G80S.
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robcurrie
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Re: Rotor question

Post by robcurrie »

Jim, on the alloy chaincase, the stator is located on it's outside diameter, not the studs.

Mikey, have you checked that the end of the crank is running true?

Rob C
mikeydpippin
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Re: Rotor question

Post by mikeydpippin »

Sorry Rob, not sure how to do this on the bike.
Looking for a you tube video to explain??
Mike
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robcurrie
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Re: Rotor question

Post by robcurrie »

The easiest way to explain is:
Does the end of the crank - where the rotor fits - wiggle around if you start the engine?
If you have a dial gauge, or some such instrument, you could measure the amount.
HTH

Rob C
Mick D
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Re: Rotor question

Post by Mick D »

robcurrie wrote:on the alloy chaincase, the stator is located on it's outside diameter, not the studs.
Hi Rob C

The stator is located by the studs on my alloy case, there is a small annular gap between the stator and case which allows for 'fine tuning' using the method mentioned above.

Regards Mick
LynP
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Re: Rotor question

Post by LynP »

I am not sure how you check rota/stator clearances on our heavyweights, as the stator is bolted inside the alloy outer case and the clearances cannot be checked until the outer case is fitted, once it is bolted up there is no access for checking the gaps. I would think as has been suggested the bearings or the shaft on the crank is out of true. Two more suggestions are; is it a dynamo crank with an retro fitted extension for the rota which is out of true or is the inner chaincase out of line some how?
mikeydpippin
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Re: Rotor question

Post by mikeydpippin »

ajscomboman wrote:Does seem to be a problem with these rotors at the moment. Take another 4-5 thou total off the rotor and it'll still be fine. I think Big Wol took nearly 7 thou of his (that's total, so 3.5 thou skim cut) and it still worked spot on.

Also, the new 74mm rotors are not so deep as the 70mm, because when tightened fully on the shaft the rotor is loose.
I had to put 2 washers crank side of rotor to pack out and allow the rotor and washer to be tightened.
Mike
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