alternator rotor on my xj (?)

[M_Ross]

I have a question for anyone who might know: I recieved a alternator rotor from ebay, but the etchings on it say Seca and its smaller in diameter by 3/4 of an inch..everything else seems to be the same (brush contact rings, thread hole).. before I go ripping my old, beat up one off, any have an idea if this will work? does the distance between rotor and stator make a difference?
Thanks for looking

Mike

[M_Ross]

pertaining to above post..there is a 1/2 inch difference (smaller) between the rotor and the stator all around

[Jerry]

Sounds to me like a case of mistaken parts identity. Many sellers don't realize that yamaha use the Maxim name on a number of models of various displacements.

I am not a guru, but doubt that the rotor you received willl work. The clearance between the rotor and outer windings has a direct impact on the current produced...has to do with the strength of the interaction between the 2 windings. Just look at a starter or automotive alternator...the clearances between the spinning and fixed windings is measured thousanths or tenths of an inch.

There should be a part number someplace on the rotor; see if it starts with 10M. If it does not I would try to return it and get my money back.

[fredintoon]

XJ's got brushes?

- - - etchings on it say Seca and its smaller in diameter by 3/4 of an inch..everything else seems to be the same (brush contact rings, thread hole).. - - -
Mike

Hi Mike,
the rotating electromagnet rotor on my XS650 has brush sliprings and all that whirling wire is failure prone.
OTOH, the rotor on my XS11 is a perforated steel ring that spins outside of a stationary electromagnet and inside the stator.
No brushes to wear out, no whirling coils to centrifuge themselves to death, neat!
But your XJ uses a wire-coil rotor with sliprings?
A great leap backwards?

[M_Ross]

Its all good guys..got 'em to right their wrong. Thanks for the input tho.

[Jerry]

But your XJ uses a wire-coil rotor with sliprings?

Yep, the XJ has a different alternator set-up than the XS. Higher output, needed because of the XJ's digital instrument cluster. The XJ system uses carbon brushes.

If you compare the right side of an XJ engine to the right side of an XS engine you will see that the XJ alternator cover extends farther out than the XS. This is due to the alternator differences.

[trbig]

If you are needing just the rotor.. not the stator.. I have a couple of those paperweights laying around here if your deal falls through.

And just for your information, the rotor and stator clearance is very critical. It's actually so close, that if you aren't careful and leave an extra chunk of gasket on the mating surfaces on one part and simply slap on another gasket and button it up.. this will leave your cover slightly cocked and your rotor will rub your stator.. ruining it in seconds. Don't ask me how I know... TWICE! Also... proper rotor installation is critical. If you simply throw the rotor on the shaft and tighten up the bolt.. it will rub and ruin your stator. Get some carb or brake cleaner, soak down the beveled crank shaft LIBERALLY.. then spray the inside mating surface of the rotor LIBERALLY. Make sure there's no specks of dust or anything. Set the rotor onto the shaft, then with a piece of wood against the face of the rotor.. or a dead blow hammer.. smack the rotor a really good shot to set it on the shaft. Only then.. screw on the bolt and get "Gootentight".


Tod

[M_Ross]

Thanks Trbig..they are sending me the right one. I will be vigilant when I put the new one on..The old one sure was a bitch to get off tho!

[trbig]

Yeah, they really are. No idea or clue as to what makes them stick so hard on an angled shaft... but stick they do!


Tod