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#399517 - 10/18/11 2:10 pm Rotor/stator clearance
desco Online   content
BritBike Forum member

Registered: 11/30/08
Posts: 1393
Loc: 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]
Stuart Online   content
BritBike Forum member

Registered: 06/12/02
Posts: 5936
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,

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#399530 - 10/18/11 3:30 pm Re: Rotor/stator clearance [Re: desco]
John Healy Online   content


Registered: 03/24/05
Posts: 8553
Loc: 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.
_________________________
"Don't just teach your children to read. Teach them to question what they read." George Carlin

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#399532 - 10/18/11 3:34 pm Re: Rotor/stator clearance [Re: desco]
JubeePrince Offline
Life member

Registered: 11/18/05
Posts: 6077
Loc: Back on the mainland!
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...

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#399539 - 10/18/11 3:52 pm Re: Rotor/stator clearance [Re: desco]
rstar45 Offline
BritBike Forum member

Registered: 09/21/09
Posts: 227
Loc: 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!

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

Registered: 11/30/08
Posts: 1393
Loc: 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.

Top
#399555 - 10/18/11 6:22 pm Re: Rotor/stator clearance [Re: rstar45]
JubeePrince Offline
Life member

Registered: 11/18/05
Posts: 6077
Loc: 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...

Top
#399567 - 10/18/11 7:40 pm Re: Rotor/stator clearance [Re: desco]
Tobin Peever Offline
BritBike Forum member

Registered: 09/23/08
Posts: 193
Loc: 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

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#399623 - 10/18/11 11:43 pm Re: Rotor/stator clearance [Re: desco]
JubeePrince Offline
Life member

Registered: 11/18/05
Posts: 6077
Loc: 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...

Top
#399650 - 10/19/11 3:13 am Re: Rotor/stator clearance [Re: JubeePrince]
Tobin Peever Offline
BritBike Forum member

Registered: 09/23/08
Posts: 193
Loc: 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

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#399685 - 10/19/11 12:17 pm Re: Rotor/stator clearance [Re: desco]
Pete R Offline
BritBike Forum member

Registered: 07/07/09
Posts: 3295
Loc: 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.

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#399686 - 10/19/11 12:18 pm Re: Rotor/stator clearance [Re: desco]
Happy Birthday Tiger Offline
BritBike Forum member

Registered: 10/26/04
Posts: 4429
Loc: 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.

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#399707 - 10/19/11 2:59 pm Re: Rotor/stator clearance [Re: JubeePrince]
rstar45 Offline
BritBike Forum member

Registered: 09/21/09
Posts: 227
Loc: 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!

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#400295 - 10/23/11 2:45 pm Re: Rotor/stator clearance [Re: rstar45]
ohio-rider Offline
BritBike Forum member

Registered: 06/02/09
Posts: 29
Loc: 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.


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#400299 - 10/23/11 3:22 pm Re: Rotor/stator clearance [Re: ohio-rider]
Tobin Peever Offline
BritBike Forum member

Registered: 09/23/08
Posts: 193
Loc: 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

Top
#400309 - 10/23/11 4:08 pm Re: Rotor/stator clearance [Re: Tobin Peever]
desco Online   content
BritBike Forum member

Registered: 11/30/08
Posts: 1393
Loc: 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.

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Untitled Document

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