Alternator rotors and spacer

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Please,
Two questions:
1.what is the difference between this two rotors? Can i use both on my 750?
2.the chamfer side (recess side) of the spacer goes against the sprocket or to the shim side? Why needs this recess?
Thank you.
Piero
Alternator rotors and spacer

Alternator rotors and spacer

Alternator rotors and spacer
 
if i recall correctly (installed few weeks ago), it needs that recess for the woodruff key to have clearance, so it can be mounted only in one way.
 
dimitri said:
if i recall correctly (installed few weeks ago), it needs that recess for the woodruff key to have clearance, so it can be mounted only in one way.
Hi.
Sorry but woodruff key is those of engine of the rotor?
In other more simply words the recess goes out to the rotor? Or into to the sprocket?
Thank you.
Piero
 
Hi pierodn.
Recess toward sprocket.
Full face against rotor centre.
Ta.
 
needing said:
Hi pierodn.
Recess toward sprocket.
Full face against rotor centre.
Ta.
Hi and thank you.
I mean.
But why there is this recess on the spacer?
Sure not for the engine key!
Ciao
Piero
 
Hi pierodn.
To ensure that the force is applied to the face of the sprocket without risk of contact with shaft taper (is my guess).
Perhaps it is a carry-over from an earlier model prior to the triplex chain being introduced.
Ta.
 
pierodn said:
But why there is this recess on the spacer?
Sure not for the engine key!
Ciao
Piero

The crank sprocket goes slight beyond the shoulder on the taper of the crank. The recess on the spacer will encapsulate this shoulder and allow the rotor nut to apply clamping force to the sprocket and its taper.

Rotor not will press against the rotor, rotor against the spacer, spacer against the sprocket over the shoulder.
 
Hi Les,
Thank you.
I mean and i think now that you said that the shims go against the sprocket that the recesse against the rotor needs to untouch the steel side of the rotor and to go agsinst the alu side only.
Please, simerging about the two rotors?
Ciao
Piero
 
I followed the original manual (recess outwards), and it is working perfect.

Would swear it was not even possible the other way around on my MK2. The woodruff key would not completely seat in the crankshaft that way. I did not try for the possibility to mount the rotor with the key sticking out a little in the front. Might have worked also.
Don't know if that is the original function for the recess, but it could. Might be cheaper to fabricate than a keyway for the spacer.
 
Oh dear.
Now I will have to pull the primary apart to have another look.
Pierodn - you had better go by the book.
Both rotors should be ok.
Ta.
 
Use the rotor on the first picture (serial number .....2298) because the rotor on the second picture (serial number ....2006) tends to explode. The later rotors have a welded centre and will not come apart.
 
pierodn said:
i think now that you said that the shims go against the sprocket that the recesse against the rotor

That's what the "books" say. Shims first, then spacer.

From the Haynes manual:

Alternator rotors and spacer



pierodn said:
the rotor needs to untouch the steel side of the rotor and to go agsinst the alu side only.

I don't think I can give you an answer to that.


pierodn said:
Please, simerging about the two rotors?

Simerging? If you are asking which rotor to use then I would say the newest one (54202298)
 

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Hi LAB.
I don't use shims so that may explain rationale for spacer reversal.
I'll have a look to check.
Does the spacer in your book press against the rotor alloy?
Ta.
 
In my 2 combats I had to face the recess towards engine to straddle the woodruff key which stuck our a bit beyond the rotor once rotor spaced to center in stator. I could not assemble my 2 Combat with the flat against the rotor - so which is correct the maual or real life facts? There are other errors in the manuals, oil tank hose route shown fatally reveresed for another one. On yeah do Not mix up-confuse the very similar looking clutch spacer part. If there is enough threads sticking out one can put this recessed spacer in backwards and still get away with it - if crank end nut stays on.
 
My spacer is recessed on both sides. One side to to cover the end of the crank that sticks out (maybe 1mm or so) from the sprocket, and the other (with smaller inner diameter that would not work if reversed) to allow for the rotor key. What's up with that, LAB?
 
Hi.
The alternator key works great with the spacer fitted both side, never touchs the key that have enough place.
Bah!
Ciao
Piero
 
nortonspeed said:
Use the rotor on the first picture (serial number .....2298) because the rotor on the second picture (serial number ....2006) tends to explode. The later rotors have a welded centre and will not come apart.

How can you tell? I heard welded ones had a "W" stamped on them. I think I had to replace the original one that came with my '73 850 because I could wiggle it on its hub, but if I did it was 18 or 19 years ago and my memory is a little fuzzy. I think the welded rotors were introduced late during Commando production.
 
ewgoforth said:
nortonspeed said:
Use the rotor on the first picture (serial number .....2298) because the rotor on the second picture (serial number ....2006) tends to explode. The later rotors have a welded centre and will not come apart.

How can you tell? I heard welded ones had a "W" stamped on them. I think I had to replace the original one that came with my '73 850 because I could wiggle it on its hub, but if I did it was 18 or 19 years ago and my memory is a little fuzzy. I think the welded rotors were introduced late during Commando production.

"Welded" rotors appear to be something of a myth:

https://www.accessnorton.com/NortonCommando/how-bad-is-it.19060/page-3#post-285005

http://www.britbike.com/forums/ubbthrea ... Post582074


http://www.oldbritts.com/11_068100.html
 
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