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steve-d
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Rotor/stator air gap...
#739082 06/18/18 2:19 pm
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MikeG Online Content OP
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I've heard from "anything as long as it's not rubbing up to has to be exactly .00?? even all the way around. Not sure what to believe.
Thanks


1960 BSA A10
2007 Suzuki Bandit
1957 A10
(Used to be a Triumph here)
71 Norton Commando
17 Triumph Bonneville

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Re: Rotor/stator air gap...
MikeG #739086 06/18/18 2:41 pm
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8 thou is the Lucas advice, but you need to test this all the way round and with the crank also turned in say 60 to 90 degree chunks in case of a slightly bent crank.

Re: Rotor/stator air gap...
MikeG #739227 06/19/18 11:56 pm
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I used a piece of thin plastic from an ice cream tub. Wrapped it around the rotor and tapped gently to locate the stator evenly.

As long as it's the same all around I think, but the closer to spec the more consistent charge you'll get ( I think ).

What can you do to change the clearance anyway? Can't change the size of the parts. Just shoot for even I reckon.


'51 C11 in a '54 C10L frame. Back on the road...
'70 Triumph Trophy 500. Next on the bench for a refresh!
'72 Triumph Tiger 650. Back on the road...
Re: Rotor/stator air gap...
MikeG #739248 06/20/18 6:34 am
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You can gently, and I repeat GENTLY, tap the mounting studs for the stator to center the rotor.
As long as the gap is at least 8 thou at any point I'm happy. Rotate a few times and check again.
Helps to have a brass feeler gauge.


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
Re: Rotor/stator air gap...
MikeG #739266 06/20/18 12:41 pm
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I have used brass feeler gauges in the past as well as a gentle tug on a studs, but I'm afraid to try again if need be. My thought is to open the mounting holes in the stator up a bit to gain some wiggle room.


1960 BSA A10
2007 Suzuki Bandit
1957 A10
(Used to be a Triumph here)
71 Norton Commando
17 Triumph Bonneville

Re: Rotor/stator air gap...
MikeG #739273 06/20/18 1:42 pm
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Hi Mike,

Originally Posted by MikeG
My thought is to open the mounting holes in the stator up a bit to gain some wiggle room.

'Fraid that's a crap idea; the stator will just "wiggle" down 'til the tops of at least two of the holes are sitting on the tops of the studs. frown 'Fraid the stator holes are a tight fit on the studs for a reason ...

Fwiw, I use a similar method to Ginge, although I use half-a-dozen bits of aluminium of the correct thickness, sticking out well beyond the face of the stator/rotor so I've got plenty to grab to pull 'em out when the job's done.

The stator can't be moved relative to the rotor with the rotor in place on the crank; the gap between it and the stator is too small to move the studs and let them 'spring' back. frown

I assemble rotor, shims and stator off the bike and then offer the whole assembly to the crank and stator studs - that immediately shows which studs don't line up with stator holes and which direction the stud/s need/s to move. What you're aiming for is the assembly to slide on to crank and all three stator studs without pushing any of the latter sideways; fitting the assembly, removing it, moving a stud, repeat is tedious but, if you don't do it any stud/s is/are pushed over fitting the assembly, when you remove the shims, the pushed stud(s) will just move the stator relative to the rotor. eek

Hth.

Regards,

Re: Rotor/stator air gap...
Stuart #739283 06/20/18 3:37 pm
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MikeG Online Content OP
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Originally Posted by Stuart
Hi Mike,

Originally Posted by MikeG
My thought is to open the mounting holes in the stator up a bit to gain some wiggle room.


I assemble rotor, shims and stator off the bike and then offer the whole assembly to the crank and stator studs - that immediately shows which studs don't line up with stator holes and which direction the stud/s need/s to move. What you're aiming for is the assembly to slide on to crank and all three stator studs without pushing any of the latter sideways; fitting the assembly, removing it, moving a stud, repeat is tedious but, if you don't do it any stud/s is/are pushed over fitting the assembly, when you remove the shims, the pushed stud(s) will just move the stator relative to the rotor. eek

Hth.

Regards,


I like this idea..as tedious as it sounds.
Thank You!


1960 BSA A10
2007 Suzuki Bandit
1957 A10
(Used to be a Triumph here)
71 Norton Commando
17 Triumph Bonneville

Re: Rotor/stator air gap...
MikeG #739391 06/21/18 3:39 pm
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If you need to tweak the studs use a deep socket with an extension on it for more leverage. Socket should be deep enough to almost reach to base of stud. This will allow you to bend the stud close to the case. Slip the socket over the stud and gently bend it. Keep checking until you have the clearance you need all of the way around. I use a .008 brass feeler gauge to check.


1978 Bonneville T140E
1974 Trident
1970 BSA Thunderbolt
1971 Norton Commando
1972 Norton Commando
1973 Norton Commando
1974 Norton Commando
2018 Kawasaki Z900RS


Everything will be alright in the end. If its not alright, its not the end.
Re: Rotor/stator air gap...
MikeG #739409 06/21/18 7:00 pm
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Well, I ended up with .010 all the way around except for one spot with .009 thou, checked at 6 different rotor locations with just a minor tweak of the studs. Not gonna sweat that .001 too much. I started it up and had 13.2V at 1200 RPM with the lights on.


1960 BSA A10
2007 Suzuki Bandit
1957 A10
(Used to be a Triumph here)
71 Norton Commando
17 Triumph Bonneville

Re: Rotor/stator air gap...
MikeG #739473 06/22/18 3:33 pm
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Hi Mike,

Originally Posted by MikeG
.010 all the way around except for one spot with .009 thou,
started it up and had 13.2V at 1200 RPM with the lights on.

thumbsup

Did you have to use a 'method' or did stator 'n' rotor just fit straight on?

Regards,

Re: Rotor/stator air gap...
Stuart #739483 06/22/18 6:28 pm
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MikeG Online Content OP
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Originally Posted by Stuart
Hi Mike,

Originally Posted by MikeG
.010 all the way around except for one spot with .009 thou,
started it up and had 13.2V at 1200 RPM with the lights on.

thumbsup

Did you have to use a 'method' or did stator 'n' rotor just fit straight on?

Regards,


Fit right on pretty well Stuart. I was going to use your method but lacked enough shim stock so I just installed everything and used a brass feeler gauge, taking 6 measurements with the rotor moved 60 degrees between each set of measures.


1960 BSA A10
2007 Suzuki Bandit
1957 A10
(Used to be a Triumph here)
71 Norton Commando
17 Triumph Bonneville

Re: Rotor/stator air gap...
Stuart #739676 06/24/18 2:59 pm
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Originally Posted by Stuart
Hi Mike,

Originally Posted by MikeG
My thought is to open the mounting holes in the stator up a bit to gain some wiggle room.

'Fraid that's a crap idea; the stator will just "wiggle" down 'til the tops of at least two of the holes are sitting on the tops of the studs. frown 'Fraid the stator holes are a tight fit on the studs for a reason ...




I suppose BSA didn't get the memo! On the BSA Unit Singles C15 through B50 they used 1/4 inch studs for mounting the alternator stators which have 5/16 inch holes. I feel fortunate that my stators never did shift around and cause rubbing problems. And the way BSA Units vibrate, it must have been a miracle!

Peter Joe


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