I replaced/upgraded my alternator in my K75RT-P about 4 weeks ago. I purchased a used 50W alternator that had been tested and was from a 29000 mile bike (according to the seller). When I replaced the alternator I thought that the monkey nuts could be reused. When I began to drive the bike there was a pronounced rattle and vibration from the right side of the bike. It was very pronounced at lower rmps when starting in first gear. At higher rmps the rattle and vibration went away. It became clear that the monkey nuts needed to be replaced after all so I ordered them from the dealer. As the bike is my daily driver I put up with the rattle and vibration for two weeks while waiting for the parts. When the parts arrived I pulled the alternator and replaced the monkey nuts. Recently, I have noticed a less pronounced vibration and rattle at start. It is similar but lower intensity to the vibration and rattle from before. I might be imagining it but it seems to be there. 

My question to the elders is: could I have damaged the alternator by running it for two weeks before parts arrived? I examined the cups and there was no noticeable damage or wear. What else could be causing the vibration and rattle?

If it is an alternator from a K1100 then you cant just put it straight in there are changes that need to be made other wise the bearing behind the drive gets lateral load and rapidly throws in the towel.
If it was from a late model K75 then all should be OK.
And check that the vanes of the drive are seated in the correct place. It' easy to get metal to metal when you put them in (dont ask) and that is very noisy.

RicK G wrote:If it is an alternator from a K1100 then you cant just put it straight in there are changes that need to be made other wise the bearing behind the drive gets lateral load and rapidly throws in the towel.
If it was from a late model K75 then all should be OK.
And check that the vanes of the drive are seated in the correct place. It' easy to get metal to metal when you put them in (dont ask) and that is very noisy.

Thanks. I have emailed the seller to determine the donor bike. I am fairly confident that the vanes are correctly separated by the monkey nuts. There was a line on the outside of the cup to line up the engine side vane with the space in the middle of the monkey nut.

klamityboy wrote:
Thanks. I have emailed the seller to determine the donor bike. I am fairly confident that the vanes are correctly separated by the monkey nuts. There was a line on the outside of the cup to line up the engine side vane with the space in the middle of the monkey nut.

Even though you believe the nuts are in the correct place, than can rotate or move a bit when putting them in. All seems fine till you start it up.
think Rick G mentioned a dab of super glue behind each nut and then a little grease (read spit or soap or nose pickings) just to help them slide in to the correct spot without moving.

RicK G wrote:there are changes that need to be made, otherwise the bearing behind the drive gets lateral load and rapidly throws in the towel.

Rick, can you elaborate?  I thought the K75 and K100 used the same dog and monkey nutz.  The K1100 alternator swap is direct for the K100; what needs changing for the K75 to prevent the lateral loading of the bearing?

I am not entirely sure what needs to be changed but the depth of the engagement of the vanes is the problem.
The 32 amp units are interchangeable but the 50 amp K1100 need the vane from a K100 with a different washer behind I think.
I put a 60 amp unit from a 1200 with the front section of the 50 amp case from a K75 and the 32 amp vane on my K1100.
Drake Smith makes a Kit for doing it.
I recall one of the guys on Motobrick.com using a K1100 50A unit and thats what it did and Drake sorted the right parts for him. That is how I remember what happened but not the solution.

THIS thread?
Is that what we are talking about?

Or THIS thread

It may be that one of Robs but I think the one I am thinking of is from Motobrick.
TWB may know more, he did say once to me that Drake goes into where he works to buy bits for the Alternator swaps. 
We'll pick his brains when he get back here.

After reading the post by robmac I am going to pull the alternator and see what is going on. Perhaps there is an errant washer under the cup that can be removed and fix the problem. Fingers crossed that it is as simple as that.

I spoke with the seller and he indicated it might be the alternator bearings even though there was only 29000 miles on the donor bike. How does one test the bearings?

Lastly, I should make it clear that the seller has offered to replace the alternator if I cannot resolve the issue. Very stand up guy.

If it is the bearings making that much noise then you will feel it by just turning the shaft by hand.

ive experianced the exact same noise on my k100, with the std.33A generator, i just recieved new nuts (for the bike that is:lol: ) and hopefully the noise will disappear when i change them tomorrow.

klamityboy wrote:I replaced/upgraded my alternator in my K75RT-P about 4 weeks ago. I purchased a used 50W alternator that had been tested and was from a 29000 mile bike (according to the seller). When I replaced the alternator I thought that the monkey nuts could be reused. When I began to drive the bike there was a pronounced rattle and vibration from the right side of the bike. It was very pronounced at lower rmps when starting in first gear. At higher rmps the rattle and vibration went away. It became clear that the monkey nuts needed to be replaced after all so I ordered them from the dealer. As the bike is my daily driver I put up with the rattle and vibration for two weeks while waiting for the parts. When the parts arrived I pulled the alternator and replaced the monkey nuts. Recently, I have noticed a less pronounced vibration and rattle at start. It is similar but lower intensity to the vibration and rattle from before. I might be imagining it but it seems to be there. 

My question to the elders is: could I have damaged the alternator by running it for two weeks before parts arrived? I examined the cups and there was no noticeable damage or wear. What else could be causing the vibration and rattle?

So a quick update. On the weekend I pulled the alternator. On the recommendation of another member of this forum I ran the bike without the alternator to get a baseline. 

I examined the alternator and the monkey nutz upon removal. The monkey nutz were in place upon removal. There was a small amount of powdered (very fine) rubber around the top edge of the cup. the monkey nutz appear to be in good shape (I would hope so since they were installed new two weeks ago). I also measured the distance from the bolt brackets to the top edge of the cup on both the new and old alternator. Unfortunately, I do not have very fine measuring devices but both appeared to be nominally 57mm from the bolt bracket to the top edge of the cup.

I was advised that the alternator bearings might be the source of the noise. I am no expert in determining whether the bearings beginning to get worn. When the new alternator was out I rotated both the new and old alternators. Both seemed similar although the old one turned slightly more freely.

Reinstalled the alternator. Started the bike and there is still a slight ticking, or rubbing noise and a slight vibration. Perhaps this is what I should expect.

Thoughts?

DID THE CLICKING AND VIBRATIONS DISAPPEAR WHE YOU DROVE WITHOUT THE ALTERNATOR?

klamityboy wrote:So a quick update. On the weekend I pulled the alternator. On the recommendation of another member of this forum I ran the bike without the alternator to get a baseline. 

I examined the alternator and the monkey nutz upon removal. The monkey nutz were in place upon removal. There was a small amount of powdered (very fine) rubber around the top edge of the cup. the monkey nutz appear to be in good shape (I would hope so since they were installed new two weeks ago). I also measured the distance from the bolt brackets to the top edge of the cup on both the new and old alternator. Unfortunately, I do not have very fine measuring devices but both appeared to be nominally 57mm from the bolt bracket to the top edge of the cup.

I was advised that the alternator bearings might be the source of the noise. I am no expert in determining whether the bearings beginning to get worn. When the new alternator was out I rotated both the new and old alternators. Both seemed similar although the old one turned slightly more freely.

Reinstalled the alternator. Started the bike and there is still a slight ticking, or rubbing noise and a slight vibration. Perhaps this is what I should expect.

Thoughts?

k-rider wrote:DID THE CLICKING AND VIBRATIONS DISAPPEAR WHE YOU DROVE WITHOUT THE ALTERNATOR?

klamityboy wrote:So a quick update. On the weekend I pulled the alternator. On the recommendation of another member of this forum I ran the bike without the alternator to get a baseline. 

I examined the alternator and the monkey nutz upon removal. The monkey nutz were in place upon removal. There was a small amount of powdered (very fine) rubber around the top edge of the cup. the monkey nutz appear to be in good shape (I would hope so since they were installed new two weeks ago). I also measured the distance from the bolt brackets to the top edge of the cup on both the new and old alternator. Unfortunately, I do not have very fine measuring devices but both appeared to be nominally 57mm from the bolt bracket to the top edge of the cup.

I was advised that the alternator bearings might be the source of the noise. I am no expert in determining whether the bearings beginning to get worn. When the new alternator was out I rotated both the new and old alternators. Both seemed similar although the old one turned slightly more freely.

Reinstalled the alternator. Started the bike and there is still a slight ticking, or rubbing noise and a slight vibration. Perhaps this is what I should expect.

Thoughts?

Didn't need to drive. The noise is there at idle. There was none of the characteristic noise with the alternator removed. When the alternator was reinstalled the noise was back. I guess I am wondering if the noise is normal or if there is something wrong with the alternator? The forum is great for all sorts of information but nothing beats an experienced ear for issues such as this.

It could be your 55amp alternator makes a noise, it could be a slight missmatch with the flange where it meets up in the monkey nuts. If you stick the 33amp unit back in and no issues appear then perhaps you can change the fanes from the 33amp unit to the 55amp unit so the monkey nuts are living in a happy place, that way if the noise still persists then it may be a noisey alternator. certainly whilst off you could have an automotive electrician give the 55map a test for health

Hi,

My experience.....

A noise like a cam chain was hitting against the case - not real bad but best way to explain it.....

I was noted by Charlie99 that the noise reduced when the Alt come under load.....  This was a good clue.....
When riding the bike was also noticeable especially when under load......

Started carting a women around on the back of her (K1100LT) last week and could hear it much more under load (no, she is not 110KG)....

Embarrassed me enough to pull her apart..
My monkeys nuts were not worn out as much as I really wanted them to be to account of the noise.....
However, when I compared the side to side movement of the Alt bearings (I have spares) I found the noisy one to have approx 1.5mm of moment side to side (the rear bearing is shot).
I ran the bike with out an Alt on it - no noise......
I am now sure its the bearing in the Alt I am swapping out.....
Easy fix.....

On a side note, I read where Charlie99 had mentioned that a failing Alt can make your TEMP gauge jump a round a little.
This swap out will give an answer to this (I hope) as I also have that problem.....

The bottom one is the one that is being swapped out - sad but not dead nuts.....