Stator Rotor relationship

I'm upgrading my old tired alterantor to a new 3PH Lucas system. Upon assembling, it seems to me the rotor is too far inboard of the stator. I realize there are shims behind the spacer collar - which I assume are to set up this relationship, but I can't find any reference to what it should be. Currently my rotor is about 5/16" inboard.
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Does this seem correct? If not, what should it be?

Thanks - David

These rotors always seem to sit far inboard, shimming doesn't really make much difference as the shims aren't thick enough to bring it out by the amount that you would imagine it needs. In my experience it doesn't seem to have any effect on the charging what the relationship of rotor to stator is within the adjustment parameters.

Thanks - I guess I can button it up now!

I have that same unit on my 850 and the surface of the rotor is just slightly below the surface of the stator. Frankly, your pic looks wrong to my eye - but as noted, if it charges OK, showing the proper voltage/RPM then it doesn't matter. I'm wondering if perhaps the washer-spacers on the three stator studs are too long though I have to admit I can't imagine how that could be.

The stator spacers seemed like the correct size, although I guess anything is possible. I just measured them - they are 0.495". What say you?

I've put in a couple Lucas 3 phase stators and the magnets and stator core aligned much better than that. Do you have your old 120w stator? Have you compared it to the 47244 stator? They should be the same thickness.

Just measured the old parts - they are within 0.010" of the new parts. In other words that doesn't seem to be it. Good question however. The stack up is engine sprocket, 2 shims, spacer (with recess outboard), rotor, fan washer, nut.

After installing a belt drive from RGM, I went to the local Ace hardware store and got shorter spacers to go behind the stator which brought it in nicely over the rotor. I had a micometer with me to make sure that all were egual (.325) as I pick them out of the bin. That's the important part. Double check all clearances upon assembly.

It may work the way you have it but I am sure you are losing some effectiveness/effeciency.

I still can't figure out why it would be so different from the original setup as the dimensions are so close. I can't help but feel I've done something stupid. New spacers could be the answer.

The stator spacers seemed like the correct size, although I guess anything is possible. I just measured them - they are 0.495".

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The spacers (060377) are 5/16 X 9/16 X 1/2, so you have the correct spacers. That is a Lucas stator and not a SPARX or Wassell?

I installed a Sparx three-phase and it looked just like that. I asked around here and a few people who'd been there and done that confirmed all was correct. That was quite some time ago, absolutely no issues since.

RonL - It is a Lucas
Ludwig - Thanks, I had been hoping someone had looked at that. Do you have any data to share? Maybe a graph?
Fred at Oldbritts thinks it's a bit too far in as well, so I'll probably tear it down, double check everything and if I can't figure it out, put in shorter spacers to get closer to centered and button it up. Thanks for all your input.

-- David

Don't the alternators on E-start and non E-start bikes differ in their location in relationship to the crankcase? Maybe some undue mixing of parts and specs makes for the misalignment. I always thought the rotor should be about flush with the stator so the magnets in the rotor align with the coils of the stator. Someone enlighten me (no pun intended).

Don't the alternators on E-start and non E-start bikes differ in their location in relationship to the crankcase? Maybe some undue mixing of parts and specs makes for the misalignment. I always thought the rotor should be about flush with the stator so the magnets in the rotor align with the coils of the stator. Someone enlighten me (no pun intended).

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The rotor and stator are the same spatially. The e-start has a longer crank snout and there is an outrigger that mounts the stator so everything is a little further out. This is straight pre-Mk3 stuff here tho, so nothing to to mix up.

Here's the update/conclusion - I did a bunch of measuring this AM and found my old rotor and stator had about the same dimensions - save for one. The overall thickness of the stator. My old one was around 1.420 - 1.440 (hard to measure as the coating was somewhat bubbled), the new one varied from 1.390 to 1.520 - quite a range. Upon further investigation, the inner surface of the stator was parallel to the inner surface of the metal flange - however the outer surface was not. In other words the outer surface looks like it was formed with what amounts to 0.150 high spot - and the high spot was pretty close to the bottom when mounted, so the visual effect is the worst there. That explains some of the appearance when mounted. Further, the offset from the metal flange to the inner surface matched my old stator.

So what I think is going on is this, my old rotor was inboard of the old stator by about 0.190. The new rotor was inboard by about .335 - measured at the bottom - a delta of 0.145. If you factor in the high spot, that explains most of the difference. It also sorta says the old combo was a bit off as well.

What I've decided to do is make new stator spacers. The current ones are 0.490 and I've turned some that are 0.305". That centered up everything and I see no clearance issues.

Here's a pic of the final product. Note that at around the 2 o'clock position, the rotor is almost flush with the stator.



Sheesh. I guess this is what you call fettling.

-- Thanks again for all the input. David

BrianK said:

I installed a Sparx three-phase and it looked just like that.

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I have a Sparx 3-phase set up on my MKIII and the stator and rotor are pretty much even with each other. No gap like in the thread starter's pics.

I've run stator/rotor clearances of as little as .003" for decades on my Combat with the same alternator components, inner chaincase and studs. The only tangible effect I've noticed is higher electrical output.


Tim Kraakevik
kraakevik@voyager.net
Three Commandos

Yes, fettling, if you own a Commando and don't like fettling, you should find a new job. I love fettling.

Dave
69S

napanorton said:

What I've decided to do is make new stator spacers. The current ones are 0.490 and I've turned some that are 0.305". That centered up everything and I see no clearance issues.

-- Thanks again for all the input. David

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I have a small Smithy 3 in 1 (lathe/mill/drillpress). Although indespensible (currently machining out a late 72 210xxx crankcase for upcoming winter swap out), the hardware store is just a 1/4 mile away.

I made an extra spacer to go behind my rotor to make it flush with the stator, and also because the collared spacer wasn't coming out over the woodruff key, so it seemed everything needed to come out a bit. I think I made the spacer about 4mm.

Anyway then I put it all on, it all looked good so I closed up the primary and started her up. It was all running fine until I heard a metal rattling sound in the primary. When I looked I realised I'd crushed the little timing marker that's attached to the primary outer case against the rotor when I put it on, and then when I'd started it the rotor had torn it off!