Charging Light

[blackcat]

Just to finish this up. I received the new rotor from MG Cycle, installed it and it charged up to 14.1 volts but the dash light was still glowing at idle rpms, then last Friday the Domino ignition/kill switch smoked out. There was some mysterious issues when revving up the engine which I could never narrow down until now.

Anyway, until I get a replacement switch which is in route and a replacement switch harness from Greg Bender, I have jury rigged the wiring so I can start the bike via the starter. The interesting thing is that the charging light goes off immediately now and I don’t see it at idle.  Now I’m wondering if this switch was the problem all along though I can’t say why,  but I might re-install the old rotor before it’s tossed just to make sure it is in fact bad.

Thanks all.

[acguzzi]

the claw on your rotor has twisted, there should be gaps between the poles, sorry for the late response but you can see that rotor is bad from the photograph, the metal poles are touching, and that is shorting out the magnetic field lines and weakening the field which reduces your output.

[blackcat]

the claw on your rotor has twisted, there should be gaps between the poles, sorry for the late response but you can see that rotor is bad from the photograph, the metal poles are touching, and that is shorting out the magnetic field lines and weakening the field which reduces your output.

Claw?

[n3303j]

Claw, the outer iron pole piece
 They should be equally spaced, not touching their mate. Can't beleve we all missed that.

[blackcat]

Claw, the outer iron pole piece
 They should be equally spaced, not touching their mate. Can't beleve we all missed that.

Oh....OK.

[acguzzi]

This is a "clawpole" rotor, The steel "pole" pieces look like claws if you imaging the rotor disassembled so you would have the shaft, two steel "claws" the copper coil and the slip rings as separate pieces. the individual steel teeth should not touch each other when the rotor is assembled, they should be equally spaced. one of them has twisted so the steel pieces are touching, that is bad.

[blackcat]

http://www.mgcycle.com/index.php?main_page=product_info&cPath=37_161&products_id=760

Now I understand after looking at my old one compared to the new one.  Wow, how does that happen? Heat?

[n3303j]

Press fit assembly. Maybe someone grabbed an out of tolerance part and built your rotor. I assume it never dragged on the stator?

[blackcat]

Press fit assembly. Maybe someone grabbed an out of tolerance part and built your rotor. I assume it never dragged on the stator?

As I posted early on, it sort of wobbled.

[chuck peterson]

That's a new one on me...geez

[acguzzi]

I wonder if you can fix it by forcing the poles apart and gluing it in place, if it moves easily then maybe it wasn't a good interference fit, I don't know if they rely on the impregnation to hold it in place. If it "failed" then obviously at some point it has moved. How did you stop the crank rotating while you tightened the alternator bolt? Not that it should really matter but if the rotor was weak to start with?

[wirespokes]

I've never seen that before either.

Usually the rotors fail due to changes in inertia. The speeding up and slowing down causes the wire to shift and eventually wear through the insulating shorting it out, or rubbing against the steel and breaking. I've wanted to take one apart, but from descriptions of how they're built it sounded daunting. Yours would probably come apart fairly easily, unfortunately. Good thing it's been removed before it did some major physical damage!

[Old Jock]

First for me too, no idea how they are assmebled, guessing I'd have thought an interference fit or better a taper

Thanks BC you've taught me something new and something else to look for

John

[blackcat]

Thanks BC you've taught me something new and something else to look for

John

John,  That’s funny. 

I haven’t had a chance to play with the rotor and see if it moves, but at this point I consider it toast. In terms of tightening it down, I’ve always just tightened it without putting the engine in gear.

[n3303j]

BMW Specs for the same rotor bolt are 14 ft/lb with dry, burr free taper. I put bike into gear and set rear brake to tighten bolt.