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Rotor Clearance #678236
12/18/16 9:57 pm
12/18/16 9:57 pm
Joined: Aug 2001
Posts: 763
USA
Dave M Offline OP
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Dave M  Offline OP
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Joined: Aug 2001
Posts: 763
USA
Fellas, what is the correct clearance between rotor and stator please?
69 T100R

If you have done this job I welcome advice on the proper workshop method(s) to adjust that clearance, stator studs into the case would seem a somewhat fragile attachment. Thanks.


66 TR6R Trophy
67 T120R Bonneville
68 BMW R60/US
69 T100R Daytona

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Re: Rotor Clearance [Re: Dave M] #678241
12/18/16 10:45 pm
12/18/16 10:45 pm
Joined: Apr 2005
Posts: 66
Tampa FL USA
S
Sam Online content
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Sam  Online Content
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Joined: Apr 2005
Posts: 66
Tampa FL USA
I've always cut up a coke can which is .004 thick, doubled it up so it's is now .008 thick and place 4 pieces at 12, 3, 6,and 9 o'clock around the rotor and tighten the rotor onto the crank. If nothing is bent or out of line the four pieces of aluminum should slide out. I'm sure there are other methods to get this accomplished and someone will share it.

Re: Rotor Clearance [Re: Dave M] #678265
12/19/16 6:55 am
12/19/16 6:55 am
Joined: Jun 2002
Posts: 10,233
Scotland
S
Stuart Offline
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Stuart  Offline
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S

Joined: Jun 2002
Posts: 10,233
Scotland
Hi Dave,

Originally Posted By Dave M
what is the correct clearance between rotor and stator please?
69 T100R

Assuming original Lucas rotor and stator, 0.008" to 0.012" between rotor and stator coil cores, if they're proud of the potting around the inner circumference of the stator.

To fit, I use a similar method to Sam - I think I read it on this forum years ago. Only information I'd add:-

. If the stator coil cores do stick out a little from the stator potting, obviously(?) the shims need to be between them and the rotor.

. Make the shims big enough that, even when they're between rotor and stator, there's plenty sticking out to get a good purchase with pliers/vise-grips.

. If the stator isn't the same clearance all the way 'round, ime it's impossible to move the stator laterally with the rotor in place; otoh, if you remove the rotor before attempting to move the stator, you risk moving the stator too far ...

. I assemble rotor, stator and shims off the bike and then attempt to slide the whole assembly cleanly on to crank and stator studs at the same time. It must be "clean"; if fitting the stator pushes one or more studs in a particular direction, as soon as you remove the shims, the "pushed" studs will simply spring back into their original position, moving the stator relative to the rotor. cry

. Fitting rotor and stator together gives a better indication of which (if any) studs need 'tweaking' and the tweak direction.

. Yes, the process can be time-consuming and frustrating mad Otoh, if the virgin you sacrificed before starting really was, the process can work first time. bigt

. Once fitted and shims removed, don't forget to turn the crank/rotor to different positions and recheck the clearances.

Hth.

Regards,

Re: Rotor Clearance [Re: Dave M] #678284
12/19/16 10:49 am
12/19/16 10:49 am
Joined: May 2010
Posts: 2,587
Illinois, USA
TR6Ray Offline

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Illinois, USA
Dave, Last year I put in a new Wassell stator and rotor. I've had an old brass feeler gage in the toolbox for many years. That made it easy to check clearance without the magnets trying to grab the gage. I had .012" clearance all around, and I turned the crank to check at about every 60° of rotation.

I didn't need to tweak the mounting studs at all, and there was really no wiggle room when installing the parts.

Good luck with it. I assume this is on your TR6?

Ray


'64 TR6R Plus some Twins from other countries (U.S., Germany, Japan)
Re: Rotor Clearance [Re: TR6Ray] #678286
12/19/16 11:41 am
12/19/16 11:41 am
Joined: Aug 2001
Posts: 763
USA
Dave M Offline OP
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Dave M  Offline OP
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Posts: 763
USA
The 500 Daytona ran poorly this past Fall, Ray. The bike is a blast to ride except when lacking the power to climb even modest inclines. Problem found to be the 15 year old Lucas rotor slipping on it's center causing the timing marks to jump wildly when using a strobe.
Has Lucas improved this problem? Hoping so, I have seen rotors labeled as "welded".

I suppose 15 years is good service. facepalm

Sam and Stuart, thanks for your comments and help. A .008 feeler gauge will insert all around and at all crank positions.
Is a bit tight @ 9 o'clock but unless cautioned here, the britbike gods have smiled w/o the sacrifice! grin



66 TR6R Trophy
67 T120R Bonneville
68 BMW R60/US
69 T100R Daytona

Re: Rotor Clearance [Re: Dave M] #678369
12/19/16 9:48 pm
12/19/16 9:48 pm
Joined: Sep 2009
Posts: 632
SEATTLE WA
S
SEATTLE GS Offline
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SEATTLE GS  Offline
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Posts: 632
SEATTLE WA
I know I will get a lot of flack for this but.....If I can get at least .006 all around I'm somewhat happy. Almost all will have a varying amount of clearance all around the rotor. Instead of pushing and prodding the studs this way and that, which always takes oodles of time with middling results, I get out the Dremel tool with a drum sander and CAREFULLY remove JUST ENOUGH. Much quicker and works great. sometimes it is just the potting material I am removing. If it is the metal I am removing only .003. I suppose I might be losing a tiny bit of output but this is not a perfect world. This way I know that the stator will not shift back to its old position and fuse to the rotor.

Re: Rotor Clearance [Re: SEATTLE GS] #678434
12/20/16 1:00 pm
12/20/16 1:00 pm
Joined: Feb 2014
Posts: 1,201
Lancaster, California
C.B.S Offline

Parts Dealer
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Posts: 1,201
Lancaster, California
Originally Posted By SEATTLE GS
I know I will get a lot of flack for this but.....If I can get at least .006 all around I'm somewhat happy. Almost all will have a varying amount of clearance all around the rotor. Instead of pushing and prodding the studs this way and that, which always takes oodles of time with middling results, I get out the Dremel tool with a drum sander and CAREFULLY remove JUST ENOUGH. Much quicker and works great. sometimes it is just the potting material I am removing. If it is the metal I am removing only .003. I suppose I might be losing a tiny bit of output but this is not a perfect world. This way I know that the stator will not shift back to its old position and fuse to the rotor.


+1 I have done so before.

Re: Rotor Clearance [Re: Dave M] #678639
12/22/16 4:08 pm
12/22/16 4:08 pm
Joined: Oct 2003
Posts: 3,695
Emsworth, sunny south of Engla...
D
dave jones Online content
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Emsworth, sunny south of Engla...
I have done this, too. I followed the Roy Bacon way and filed metal off the pole pieces in the stator to get the right clearance which sounds like Seattle GS's technique. You can't take metal off the rotor because you may unbalance it or make it fall apart. Worked fine and is still charging fine.
Dave

Last edited by dave jones; 12/22/16 4:10 pm.
Re: Rotor Clearance [Re: Dave M] #678670
12/22/16 9:15 pm
12/22/16 9:15 pm
Joined: Jan 2014
Posts: 2,176
South cone
R
reverb Offline
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South cone
...so what s exactly the problem to have an small clearance in one side and more on the other? Still clearance...
The studs are straight and the stator fits perfectly well there.
I understand what Stuart is saying; I remember that I did something similar, but you never finish with a tight stud...so I fastened to the case but I have that variant in the clearance.

Re: Rotor Clearance [Re: Dave M] #678686
12/23/16 1:15 am
12/23/16 1:15 am
Joined: Feb 2006
Posts: 699
Qld, Aust and Otago,NZ
G
Ginge Offline
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Qld, Aust and Otago,NZ
I've got variable clearance too. Got it as close as I could, then tightened it up. May have tapped a stud with a hammer to convince it to stay there. I used the coke can trick as well.

Still runs a 55watt headlight globe. It's a Sparx unit not Lucas.

Same bike.


Ginge
Re: Rotor Clearance [Re: Dave M] #678778
12/24/16 5:09 am
12/24/16 5:09 am
Joined: Sep 2009
Posts: 632
SEATTLE WA
S
SEATTLE GS Offline
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SEATTLE GS  Offline
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Posts: 632
SEATTLE WA
there is nothing wrong with varying clearances around the rotor. Its the minimum clearance that's important. Too close and it is possible to weld the stator to the rotor. Much damage can occur.

Re: Rotor Clearance [Re: Dave M] #678813
12/24/16 3:06 pm
12/24/16 3:06 pm
Joined: Mar 2005
Posts: 10,218
Boston, Massachusetts
J
John Healy Offline

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John Healy  Offline

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J

Joined: Mar 2005
Posts: 10,218
Boston, Massachusetts
Originally Posted By Stuart
Once fitted and shims removed, don't forget to turn the crank/rotor to different positions and recheck the clearances.


This cannot be over emphasized!

Over the years the unit construction model primary covers of many Triumphs have been hit in the front. This can bend studs and crankshaft. In this condition you can offer a new stator and rotor with the bent crankshaft facing toward the back (the same way the studs are bent) giving you the impression you have clearance. When you rotate the motor 180 the clearance will to go away. Now you get out your dial indicator and check the rotor to make sure the crankshaft isn't bent. It only takes a little bit to cause problems.

Beside a bent crankshaft there are several other reason the rotor can touch the stator with disastrous results:
Loose rotors - where the zinc casting has come loose from the steel center allowing the magnets to wedge outward. This is not something to play around it. The magnets sit on a portion of the steel center that has been cut in a hexed. Each one of the magnets sit on one of the flats. When the outer part of the rotor comes loose the magnets are forced outward. The looser it gets the closer it gets to the stator. In the worse case the whole unit explodes with magnets going here and there.

Failing drive side main bearing with too much clearance. This can cause the rotor to rub with similar problems.

Non-unit models are especially problematic. On a Triumph there are only three 1/4" screws holding the inner primary cover in place. When the inner cover comes loose the stator is allowed to drop onto the rotor.

Nortons have a similar problem.


Re: Rotor Clearance [Re: John Healy] #678895
12/25/16 4:41 pm
12/25/16 4:41 pm
Joined: Sep 2009
Posts: 632
SEATTLE WA
S
SEATTLE GS Offline
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Posts: 632
SEATTLE WA
And "bent crankshaft" = "scrap crankshaft"?

Re: Rotor Clearance [Re: Dave M] #678903
12/25/16 7:53 pm
12/25/16 7:53 pm
Joined: Dec 2013
Posts: 4,396
ohio, usa
kevin roberts Offline

fefsa
kevin roberts  Offline

fefsa

Joined: Dec 2013
Posts: 4,396
ohio, usa
used ones aren't expensive

ebay crank


"Are bikes so nice as all that?" asked the mole, shyly...

"Nice? They're the only thing," said the Water Rat Solemnly, as he leaned forward on the handlebars. "Believe me, my young friend, there is nothing -- absolutely nothing -- half so much worth doing as simply messing about with bikes."
Re: Rotor Clearance [Re: Dave M] #678908
12/25/16 8:33 pm
12/25/16 8:33 pm
Joined: Mar 2005
Posts: 10,218
Boston, Massachusetts
J
John Healy Offline

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John Healy  Offline

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Boston, Massachusetts
Straightening crankshafts is normal practice.
John


Re: Rotor Clearance [Re: kevin roberts] #678931
12/26/16 7:49 am
12/26/16 7:49 am
Joined: Oct 2012
Posts: 3,991
Running from demons in WNY
Hillbilly bike Online content
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Hillbilly bike  Online Content
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Posts: 3,991
Running from demons in WNY
Originally Posted By kevin roberts
used ones aren't expensive

ebay crank


Yes cheap to buy and then cheap becomes expensive after machining the beat up right side oil feed and turning the crank to .010 as one journal is worn and the other larger than stock grin


I ride dinosaurs that eat money
Re: Rotor Clearance [Re: Hillbilly bike] #678932
12/26/16 8:30 am
12/26/16 8:30 am
Joined: Dec 2013
Posts: 4,396
ohio, usa
kevin roberts Offline

fefsa
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Posts: 4,396
ohio, usa
Originally Posted By Hillbilly bike

Yes cheap to buy and then cheap becomes expensive after machining the beat up right side oil feed and turning the crank to .010 as one journal is worn and the other larger than stock grin


you're talking about that one i have by the workbench


"Are bikes so nice as all that?" asked the mole, shyly...

"Nice? They're the only thing," said the Water Rat Solemnly, as he leaned forward on the handlebars. "Believe me, my young friend, there is nothing -- absolutely nothing -- half so much worth doing as simply messing about with bikes."
Re: Rotor Clearance [Re: kevin roberts] #678935
12/26/16 9:40 am
12/26/16 9:40 am
Joined: Oct 2012
Posts: 3,991
Running from demons in WNY
Hillbilly bike Online content
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Hillbilly bike  Online Content
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Running from demons in WNY
Originally Posted By kevin roberts
Originally Posted By Hillbilly bike

Yes cheap to buy and then cheap becomes expensive after machining the beat up right side oil feed and turning the crank to .010 as one journal is worn and the other larger than stock grin


you're talking about that one i have by the workbench
That would include the cranks in my dual engine currency convertor..
And one of the cranks had to be straightened...It was done on specialized equipment, a sort of controlled peening procedure...


I ride dinosaurs that eat money
Re: Rotor Clearance [Re: Dave M] #678964
12/26/16 3:54 pm
12/26/16 3:54 pm
Joined: Sep 2009
Posts: 632
SEATTLE WA
S
SEATTLE GS Offline
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Posts: 632
SEATTLE WA
So I will reword it..."bent crankshaft" = "expensive crankshaft"

Re: Rotor Clearance [Re: SEATTLE GS] #678968
12/26/16 4:37 pm
12/26/16 4:37 pm
Joined: Oct 2012
Posts: 3,991
Running from demons in WNY
Hillbilly bike Online content
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Hillbilly bike  Online Content
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Running from demons in WNY
Originally Posted By SEATTLE GS
So I will reword it..."bent crankshaft" = "expensive crankshaft"


Not necessarily...it cost me 40 bucks to have the crank straightened...The shop was doing machine work on the two engines so the price might have been discounted a bit...


I ride dinosaurs that eat money
Re: Rotor Clearance [Re: Dave M] #678972
12/26/16 5:35 pm
12/26/16 5:35 pm
Joined: Jun 2007
Posts: 6,026
Maui Hawaii
HawaiianTiger Online content
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Maui Hawaii
Should be included in the cost of nitriding the crank.

Cheers,
Bill


Bikes
1974 Commando
1985 Honda Nighthawk 650
1957 Thunderbird/T110 "Flying Tiger"
Antique Fans: Loads of Emersons (Two six wingers) plus gyros and orbiters.
Re: Rotor Clearance [Re: HawaiianTiger] #678982
12/26/16 8:02 pm
12/26/16 8:02 pm
Joined: Oct 2012
Posts: 3,991
Running from demons in WNY
Hillbilly bike Online content
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Hillbilly bike  Online Content
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Posts: 3,991
Running from demons in WNY
Originally Posted By HawaiianTiger
Should be included in the cost of nitriding the crank.

Cheers,
Bill


Nitriding was $116 for both cranks, it's priced by weight..One crank bent, one did not.The straightening is as needed I suppose..I had two other cranks treated in the last few years that didn't warp/bend...The bend was less than .002
The heat treating also caused the crank journals to grow slightly in diameter...About .0003 on the 1.6 inch rod journal. The machinist has to include this on junk like mine where the crank is ground to clearance before treatment based on the bearing torqued in the rod..
The Mahle rod bearings varied in diameter a few 10 thousands of an inch...


Last edited by Hillbilly bike; 12/26/16 8:14 pm.

I ride dinosaurs that eat money

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