Motorrad Elektrik aftermarket rotor?

[oldcamper]

Years ago I bought a new aftermarket alternator rotor from Motorrad Electrik as a spare for my R100gs.
The other day I tried to install it but it doesn’t seem to fit the tapered end of the crankshaft correctly. When the original is in place, it fits snugly even without the retaining bolt, but the replacement has a bit of “wobble” to it, perhaps indicating the taper is not machined correctly. The inside tapered bore is clean and free of any obvious defects.

Has anyone else ever seen this? Is this a common problem with aftermarket rotors?

 

[stevenrankin]

I haven't installed an after market rotor for a stock charging system. By that I mean to provide the stock charge rate, so a direct factory replacement rotor from a non factory source.
However, I have installed a higher output charge rotor for a high output charge system similar to the factory rotor. No problems as you are experiencing. I have also installed a brushless charging system from EME on my current project bike and have not seen a wobble as you are.

It might be a good time to give EME a call and see what they say. LOL, does what I write make sense? Good luck, St.

 

[20774]

Does EME have a part number for the R100GS? I don't see anything, but maybe they're all the same around that year??

Motorrad Elektrik used to advertise that they would sell a rewound rotor but I don't see that just now on the website.

 

[oldcamper]

Does EME have a part number for the R100GS? I don't see anything, but maybe they're all the same around that year??

Motorrad Elektrik used to advertise that they would sell a rewound rotor but I don't see that just now on the website.

I believe the 247 rotors are all mostly interchangeable, especially WRT newer stators. Later “improved” rotors have a bit lower resistance for better output but I think the tapers are unchanged.

I still have the Motorrad Electrik receipt and see the price has remained at $125 all these years, but I am a bit reluctant to just purchase another not knowing if it would fit any better than the one I currently have. A wobbly rotor would probably induce vibration and might even damage expensive or other hard to replace components. The old one still works so I put it back on but no longer have what I trust is a good spare.

 

[20774]

I wonder if EME would have some insight, even if it's been a period of time.

 

[stevenrankin]

The rotors have been pretty much interchangeable for years and years, no special part for the GS bikes. Sadly, yes, one can buy rarely bad new parts. it is rare but happens. Sorry to read you are having the problem. LOL, at least you didn't break down, and find the bad rotor then.
I will say that in the later years, rotor failure is getting pretty rare. There was a time when BMW got a lot of questionable units and for a several year period a lot got replaced due to failure.

Now a day, I look at the parts EME is selling versus Max and scratch my head wondering if they don't come from the same source? St.

 

[oldcamper]

I went to take a photo of the rotor and receipt to send to EME and to my great embarrassment see the order was placed with Motorrad Electrik, not EME.
My apologies but it was quite a while ago and I AM getting old. I have corrected my entries in this thread and will probably just purchase a used rotor from eBay to keep as a spare since I don’t ride that bike much anymore.

 

[stevenrankin]

If I had a dollar for every mistake I made when replying to people in the forums, I would be riding a new BMW bike. In reality, I wouldn't worry about a bad rotor, the GS bikes came out after the fiasco with the bad ones from BMW. St.