1 Engine Clatter Sat Sep 26, 2015 4:30 pm
MLR
active member
My 1991 K75RT (126000 km) has developed a bad clattering sound between 3500 and 3700 rpm in all gears. It’s as if someone was hitting the ‘inside of somewhere’ with several hammers. Running on the flat and level in that rpm range it is not noticeable but if the road gradient increases in that range, putting a greater load on the engine, the noise starts. It also starts if I accelerate slowly up through that range. It is not there during a rapid acceleration through that range.
I’ve gone through a number of the threads in this site on engine/alternator noise and have followed much of the good advice I’ve come across. Here’s what I’ve done so far.
The first thing was to change the alternator’s rubber shocks (monkey nuts) although the old ones didn’t appear to be particularly worn. I also changed the brushes as they were at their limits. On reinstallation of the alternator the noise was still there.
Took the alternator out again and changed the bearings (which were worn) and did a general cleanup. On re-installation the noise was still there. It may be a little less noticeable but possibly only because I’d like it to be.
In order to be able to try to home in on the noise I had hoped to get it to appear with the bike running while on its centre stand, in gear, in the rpm range, and with the rear brake dragging to try to replicate being on the road. No success.
Next step was I took the alternator out and ran the bike without it. The noise was gone!
However, I don’t quite see how such a noise could be coming from the alternator, particularly after it had been serviced. I had a look at the timing chain a couple of years back and it was in pristine condition so I don’t think it’s that. My thoughts are, and they’re based on the info I’ve read on this site, that it may be coming from the auxiliary alternator drive. Could it be that without the alternator installed there isn’t the load on it to cause it to make the noise?
There was a thread started about a year ago that sounded similar to my situation but the final outcome was never posted.
The sound in this youtube reference: www.youtube.com/watch?v=LdSNT4WPxBc sounds very much like my problem. Not the spinning sound, but the metalic ‘clank’ that’s generated.
As I’m feeling reasonably sure, well, sort of sure, well, I’m not really sure, it’s not the alternator I guess I have a winter project ahead of me.
Any thoughts or advice on the above would be greatly appreciated!
If the general concensus is that it may be the alternator drive, taking the final drive/transmission/clutch out is not an issue as I’ve done it a number of times to grease the splines, but can I get to the alternator drive without removing the engine? That seems like a pretty daunting task to me.
Once again, any thoughts or advice please.
I’ve gone through a number of the threads in this site on engine/alternator noise and have followed much of the good advice I’ve come across. Here’s what I’ve done so far.
The first thing was to change the alternator’s rubber shocks (monkey nuts) although the old ones didn’t appear to be particularly worn. I also changed the brushes as they were at their limits. On reinstallation of the alternator the noise was still there.
Took the alternator out again and changed the bearings (which were worn) and did a general cleanup. On re-installation the noise was still there. It may be a little less noticeable but possibly only because I’d like it to be.
In order to be able to try to home in on the noise I had hoped to get it to appear with the bike running while on its centre stand, in gear, in the rpm range, and with the rear brake dragging to try to replicate being on the road. No success.
Next step was I took the alternator out and ran the bike without it. The noise was gone!
However, I don’t quite see how such a noise could be coming from the alternator, particularly after it had been serviced. I had a look at the timing chain a couple of years back and it was in pristine condition so I don’t think it’s that. My thoughts are, and they’re based on the info I’ve read on this site, that it may be coming from the auxiliary alternator drive. Could it be that without the alternator installed there isn’t the load on it to cause it to make the noise?
There was a thread started about a year ago that sounded similar to my situation but the final outcome was never posted.
The sound in this youtube reference: www.youtube.com/watch?v=LdSNT4WPxBc sounds very much like my problem. Not the spinning sound, but the metalic ‘clank’ that’s generated.
As I’m feeling reasonably sure, well, sort of sure, well, I’m not really sure, it’s not the alternator I guess I have a winter project ahead of me.
Any thoughts or advice on the above would be greatly appreciated!
If the general concensus is that it may be the alternator drive, taking the final drive/transmission/clutch out is not an issue as I’ve done it a number of times to grease the splines, but can I get to the alternator drive without removing the engine? That seems like a pretty daunting task to me.
Once again, any thoughts or advice please.
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1991 K75RT (since new)
Past bikes: Triumph Bonneville 650, Triumph Bonneville 750, Triumph Trident 750, Moto Guzzi T4 850, BMW K75C