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#399517 - 10/18/11 2:10 pm Rotor/stator clearance  
Joined: Nov 2008
Posts: 2,316
desco Online content
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desco  Online Content

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Posts: 2,316
Bishop, Calif.
Is there some way to move the stator to achieve the proper .008" all the way around? I had a tight spot at about the 10 o-clock position and was loose on the opposite side. Was trying to bend the stator bolts with a deep socket on the nut and a 12" extension. SNAP. $16.75 down the toilet. The tight spot was .006 and the loose was .011 and they stayed at 10 and 4 while I turned the crank.


1968 T120R
1972 T120RV
Any advice given is without a warranty expressed or implied.
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#399524 - 10/18/11 3:14 pm Re: Rotor/stator clearance [Re: desco]  
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Stuart Online content
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Stuart  Online Content
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Scotland
Hi,

Originally Posted By: desco
trying to bend the stator bolts with a deep socket on the nut and a 12" extension. SNAP.

shocked I'm not surprised; with that amount of leverage, I'd consider myself lucky I didn't "SNAP" something a lot more expensive.

Originally Posted By: desco
Is there some way to move the stator to achieve the proper .008" all the way around?

Ime, trying to move studs individually to get 8 thou.-ish all round is a definition of futility. Thanks to advice I read on here some time ago, I find some can metal that's slightly under the necessary thickness, wrap some of it 'round the rotor, fit it in the stator and mount the whole assembly to crank and studs at the same time; that way, the correct relationships between all the bits are established at the same time.

Why "slightly under the necessary thickness"? So you can pull it out when you're done. wink

Hth.

Regards,

#399530 - 10/18/11 3:30 pm Re: Rotor/stator clearance [Re: desco]  
Joined: Mar 2005
Posts: 9,713
John Healy Online content
John Healy  Online Content



Joined: Mar 2005
Posts: 9,713
Boston, Massachusetts
Quote:
Thanks to advice I read on here some time ago, I find some can metal that's slightly under the necessary thickness, wrap some of it 'round the rotor, fit it in the stator and mount the whole assembly to crank and studs at the same time; that way, the correct relationships between all the bits are established at the same time.


Sounds like a rational idea, but it begs the question. While this might align a non-unit Triumph or Norton with all of the Concentric circles that need to be aligned, on the bikes listed in the signature it will not improve things.

It would have to bend the stator studs and/or the crankshaft for it to work. A lot of the fixed primary bikes have been damaged in an accident. This means that both the studs and the end of the crankshaft can be bent. Fixing this is best done while the engine is apart. Failing that, where you only need to gain a few thousandths, you can turn a couple off the diameter of the rotor.


#399532 - 10/18/11 3:34 pm Re: Rotor/stator clearance [Re: desco]  
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JubeePrince Online content
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desco -

I just did mine last month. Used a soft-brass hammer, worked well. Didn't take much force at all to move the stud(s) a couple/few thousandths. Took about 3 -4 tries to get it where I wanted it.

I suppose a small block of hardwood and regular hammer would work as well. The idea being *small* blows, fit and re-check clearance.

Not sure what type of steel they use these days for those studs. Mine are factory original.

Steve


'77 T140J
"Vintage Bike". What's in your garage?

"The paying customer is always right."

Fitting round pegs into square holes since 1961...
#399539 - 10/18/11 3:52 pm Re: Rotor/stator clearance [Re: desco]  
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rstar45 Offline
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Colorado
Originally Posted By: desco
The tight spot was .006 and the loose was .011 and they stayed at 10 and 4 while I turned the crank.


So the crank and rotor are turning true... Is .006 really insufficient clearance??? Are we just being anal?

I don't know so I'm asking!

#399542 - 10/18/11 4:21 pm Re: Rotor/stator clearance [Re: rstar45]  
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desco Online content
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desco  Online Content

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Bishop, Calif.
Originally Posted By: rstar45
Originally Posted By: desco
The tight spot was .006 and the loose was .011 and they stayed at 10 and 4 while I turned the crank.


So the crank and rotor are turning true... Is .006 really insufficient clearance??? Are we just being anal?

I don't know so I'm asking!


I don't know either. I would rather just leave it alone.


1968 T120R
1972 T120RV
Any advice given is without a warranty expressed or implied.
#399555 - 10/18/11 6:22 pm Re: Rotor/stator clearance [Re: rstar45]  
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JubeePrince Online content
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JubeePrince  Online Content

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Back on the mainland!
Originally Posted By: rstar45

Is .006 really insufficient clearance???

I don't know so I'm asking!


I don't know the answer to that either....everything I've read on here by guys whose thoughts and opinions I trust say .008"

I got that figure on mine with the stock Lucas rotor and 180W Sparx single-phase stator.

Steve


'77 T140J
"Vintage Bike". What's in your garage?

"The paying customer is always right."

Fitting round pegs into square holes since 1961...
#399567 - 10/18/11 7:40 pm Re: Rotor/stator clearance [Re: desco]  
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Tobin Peever Offline
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Tobin Peever  Offline
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Pullman, Washington, USA
Make sure you have at least 0.008 all the way around or rotor will lock to stator once it heats up and you will destroy your primary drive.


47 Norton ES2
61 Norton Dominator 88
67 Triumph TR6C
68 Moto Guzzi V700
74 Norton Commando
08 Moto Guzzi 1200 Sport
#399623 - 10/18/11 11:43 pm Re: Rotor/stator clearance [Re: desco]  
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JubeePrince Online content
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Back on the mainland!
I pulled the stator off to access the inner primary and didn't think to check clearance. I wrongly assumed because it was true when I took it off (it had been on there since Dec, 1976!), that it would be true when I put it back on....a thousand miles later my charging system goes belly up, the results of which can be seen below. I got lucky, it could have been worse.



Steve


'77 T140J
"Vintage Bike". What's in your garage?

"The paying customer is always right."

Fitting round pegs into square holes since 1961...
#399650 - 10/19/11 3:13 am Re: Rotor/stator clearance [Re: JubeePrince]  
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Tobin Peever Offline
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Tobin Peever  Offline
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Pullman, Washington, USA
Yep, same for me except I blew apart the primary on my Commando. That was an expensive mistake. Now I am VERY careful to make sure I have 0.008 ALL the way 'round.


47 Norton ES2
61 Norton Dominator 88
67 Triumph TR6C
68 Moto Guzzi V700
74 Norton Commando
08 Moto Guzzi 1200 Sport
#399685 - 10/19/11 12:17 pm Re: Rotor/stator clearance [Re: desco]  
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Pete R - R.I.P. Offline
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Pete R - R.I.P.  Offline
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Vic. Australia
Less rotor runout make this easier.If the rotor doesn't sit square,carefully file the high spot on the back face.It can make the difference between 0.004" runout and zero.
I always just whack the studs with a plastic hammer,one or two at a time (remove the stator first).Move one stud 0.006" and the stator moves 0.002".How easy.

You should get 0.008" clearance everywhere for a full engine rotation.I like to see a little more at the rear of the rotor,to allow for shaft flex under load.

Turning the rotor is messy,even with compressed air to blow the chips away from the magnets.It could be easier to just grind a little off the stator laminations ,if necessary.

#399686 - 10/19/11 12:18 pm Re: Rotor/stator clearance [Re: desco]  
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Tiger Offline
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Tiger  Offline
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Melbourne Australia
Trying to bend a steel stud screwed into a 40 + year old alloy crankcase seem unwise to me.


1969 TR6R
7.62 x 51 is not a maths puzzle.
#399707 - 10/19/11 2:59 pm Re: Rotor/stator clearance [Re: JubeePrince]  
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rstar45 Offline
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rstar45  Offline
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Colorado
Nice picture Steve.

Seems the consensus is "Better Safe Than Sorry!"

From turning a couple thou off the rotor, gently bumping the studs, or grinding the stator I suppose one better get his .008.

Glad I asked!

#400295 - 10/23/11 2:45 pm Re: Rotor/stator clearance [Re: rstar45]  
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ohio-rider Offline
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N.E. Ohio
Iíve had good luck just wrapping a piece of paper around the stator and slowly tightening each stud while being sure that the paper stays loose. If the paper gets tight when tightening one, move to the one on the opposite side until the paper loosens again. Repeat until all three studs are tight.


#400299 - 10/23/11 3:22 pm Re: Rotor/stator clearance [Re: ohio-rider]  
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Tobin Peever Offline
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Tobin Peever  Offline
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Pullman, Washington, USA
Originally Posted By: ohio-rider
Iíve had good luck just wrapping a piece of paper around the stator and slowly tightening each stud while being sure that the paper stays loose. If the paper gets tight when tightening one, move to the one on the opposite side until the paper loosens again. Repeat until all three studs are tight.




Yep. I have used a beer can cut into strips. US beer cans are just about the right thickness!


47 Norton ES2
61 Norton Dominator 88
67 Triumph TR6C
68 Moto Guzzi V700
74 Norton Commando
08 Moto Guzzi 1200 Sport
#400309 - 10/23/11 4:08 pm Re: Rotor/stator clearance [Re: Tobin Peever]  
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desco Online content
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desco  Online Content

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Bishop, Calif.
Well, the new stator bolt finally arrived, so much for priority mail. I noticed the other existing long bolt was slightly bent in the correct direction so I moved it to the top position and put the new one in the bottom. I had almost the correct clearance on the first try. Took it apart and GENTLY tapped the bolts with a plastic hammer, no 12" pry bar, and was done. Thanks for all the suggestions. Now on to the the 68 which has fried the stator for the second time in three years.


1968 T120R
1972 T120RV
Any advice given is without a warranty expressed or implied.

Moderated by  John Healy 


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