Rotor/Stator clearance

Hi.
You know that the stator is fitted on the outer primary cover.
How do you check the correct clearance between stator and rotor?
Thank you.
Piero

You don't!
I burned two alternators on mine, finally found one with extra clearance - went to a friend's shop and went through several of his rotors until I found the smallest, then carefully sanded the inside of the stator until I had added about .01 inch extra clearance.

Hi Bill,
i understand.
I had this problem with my Commando and so fear it.
Thank you
Piero

BillT said:

You don't!
I burned two alternators on mine, finally found one with extra clearance - went to a friend's shop and went through several of his rotors until I found the smallest, then carefully sanded the inside of the stator until I had added about .01 inch extra clearance.

Click to expand...

Hi.
Do you think could be a bad idea reducing with lathe the rotor thickness?
Thanks.
Piero

I would try paint on the stator poles, assemble, spin the engine, disassemble, and look for evidence of rubbing on the stator poles. Perhaps it would be best to do this with the paint still wet.

Minimum rotor/stator clearance is 0.005. Paint will reduce clearance by about 0.002, so it would be best to remove paint after the test.

Slick

Hi.
I can see that the three studs that are bolted into the outer primary case are thinner that the holes of the stator.
The Commando studs are of the same widht of the stator, not the P11.
May be i need a stator with small stator holes?.
Thanks.
Piero

pierodn said:

Hi.
I can see that the three studs that are bolted into the outer primary case are thinner that the holes of the stator.
The Commando studs are of the same widht of the stator, not the P11.
May be i need a stator with small stator holes?.
Thanks.
Piero

Click to expand...

Those smaller diameter studs are most likely for adjustment of the clearance.

If you match diameter of holes with studs, you still have problem of checking clearance.

Try the following procedure:

1) obtain 0.005 steel shim stock about 10 to 12 mm wide.
2) bend shim stock into "L" shape with 10 mm on short leg, and width of rotor on long leg. Make three.
3) place shims on rotor magnets 120 degrees apart, with short leg towards rotor nut.
4) note alignment of stator poles in outer cover. rotate engine so shims are in registry with three of the stator poles.
5) tighten stator nuts slightly more than finger tight. The object is to allow the stator to center itself over the shims, but not move when the cover is removed.
6) place outer cover on inner cover, being careful to have stator poles slip over shims, tap outer cover to settle everything.
7) remove outer cover, tighten stator nuts, remove shims.

Hope this works.

Slick

On the AMC outer primary, the casting is machined to accept the stator - there is NO movement. Yes the stator holes are a bit bigger than the studs, but that does not allow one to move the stator around, it allows one to wiggle the stator into place.

The outer cover also has no adjustment against the inner cover. Between the 2 locating pins and the 14 (!) screws that attach the outer to the inner cover, one cannot adjust the clearance - just trust that English engineering has perfectly centered the rotor with the stator through its precision casting and machining.

In my case, I wrapped the rotor with two layers of masking tape, carefully cutting the tape to create exactly two complete layers. I then dusted the inner surface of the stator with spray paint. I joined the two halves and spun the engine several times - any tight spots showed by rubbing the paint off the stator. I carefully sanded those high spots until I got no touches.

Its a time-consuming process, but well worth it, IMO

Commando alternator is so much easier.

Hi and thank you.
I will do it.
Piero

Rotor/stator arrangement is the biggest default of these bikes.
That burning smell is terrible. Learned a new lesson today.

Better to check it each time when removing the cover, rotor or pinion.

I assumed it would still be OK but the thickness of adding a gasket can throw the clearance off. Previously, it was run with only threebond gasket maker, no gasket.

Definitely could use a better non-stick gasket for this primary!!

The gasket doesnt make it wrong.

I know it seems strange but that is the only change from before. I removed the chain, rotor and pinion to access and reseal the 3 tapered screws. Maybe the screws became re positioned but they are tapered.


I will turn down the rotor and use the scotch or painters tape method next time, and every time.

elefantrider said:

I know it seems strange but that is the only change from before. I removed the chain, rotor and pinion to access and reseal the 3 tapered screws. Maybe the screws became re positioned but they are tapered.


I will turn down the rotor and use the scotch or painters tape method next time, and every time.

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Regrind 0,1 mm the rotor.

Makes one wonder if AMC did or did not have some sort of cut away primary cover like the cut away timing cover – I have no idea if that would work, but I doubt it.

I would think you could use some non-metallic shims (like 0.010 tho cardboard) that would wear away when rotor is turning.

Are all used original stators the same and OK for use on P11s? They all look the same. Only difference I can see is number of wires, 2 or 3.

elefantrider said:

Are all used original stators the same and OK for use on P11s? They all look the same. Only difference I can see is number of wires, 2 or 3.

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Almost yes.
But you must use one phases six faces stator.
Early stators had three wires but was one phases the same.
Look at faces, nine is three phases.