Alternator noise

[Bendy toy]

My bike today developed a whirring noise from under the petrol tank. It was pretty serious when started but faded to no noise after running for a few minutes. Output volts normal.
I'm thinking its alternator shaft bearings.
Does anyone know if the bearings can be replaced and of so what size are they.
I use the bike most days so want to strip the bike, do the job and rebuild in one hit.
Thanks


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[mikeyboy]

Alternator housing cracked due to corrosion?

 

[Ted]

Take the cover and belt off. Looking at past threads should be an easy job for you . Can spin the alternator and assess the noise/feel. Had similar, proper noisy when starting from cold, and found the belt worn and shiny so replaced it. Was well inside its service life but was ok with new belt fitted. If alternator on its way can identify the correct parts while your their then get everything and as you say do it in one hit.

 

[Posh Pete]

Slipping belt? Had you washed it?

 

[G5RJO]

It'll get worse and worse... belt off and try and turn the alternator over.

Do it cold. Not after a run so everything is freed off.

I agree with Mikeyboy. It'll be cracked ... F'd. Been there done it...

Pain in the arse job as front shock has to come off to get it out.

Roger.

 

[dashfixer]

Do you think that GS's talk telepathically to each other? Mine started doing the exact same thing this morning!
After approx 30 seconds with the engine running it stopped.
I'll listen for it tonight when I go home.
Let us know if you do strip it down as I was thinking of doing the same.
Rich

 

[Steptoe]

Do you think that GS's talk telepathically to each other? Mine started doing the exact same thing this morning!
After approx 30 seconds with the engine running it stopped.
I'll listen for it tonight when I go home.
Let us know if you do strip it down as I was thinking of doing the same.
Rich

Was it screeching before stopping after 30 seconds ? if so most of the time it means it's time for a new belt.

If the case has cracked it usually means the belt is slipping on the pulley as the commutator can't rotate which also means the alternator isn't charging the battery.

Had a fine example in last week. Came in with charging problems, but no noise at all from the belt being polished smooth as it whizzed around the seized pulley.

Bike used all year round and now with 127K miles so it lasted well.

 

[Pukmeister]

A few months ago I had belt noise for 30 secs on starting (despite a recent belt change). Liberally sprayed it with ACF50 once warm, hasn't happened since.

I'm going to remove the front shock soon and send it off for refurb so will check the alternator for cracking once removed, thanks for the photo Neil.

 

[Rusty Bolts]

My alternator occasionally used to screech when I started it. I asked CWs to look at it and the chassis was cracked like the example Steptoe posted and one of the magnets had dropped off. All changed under the BMW extended warranty.

 

[Bendy toy]

Update
The alternator was quiet today and still charging with everything on.
The noise was a whirring buzz sounded like dry bearings chattering. There was no screech and no rubbery smell.
My old vacuum cleaner sounded similar shortly before its bearings seized up.
Does anyone know the alternator bearing sizes so I can buy in advance.


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[mikeyboy]

Update
The alternator was quiet today and still charging with everything on.
The noise was a whirring buzz sounded like dry bearings chattering. There was no screech and no rubbery smell.
My old vacuum cleaner sounded similar shortly before its bearings seized up.
Does anyone know the alternator bearing sizes so I can buy in advance.


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Fit a Bosch one if you can find one.
Good upgrade

 

[Bendy toy]

Hi Mike. I think it's already got the Bosch.

It's been fine ever since that one time, but I think the bearings are on the way out. Last time I looked (a month ago) the casing looked fine. But to be fair I wasn't checking for alternator issues.

 

[Pukmeister]

I got around to removing the front shock for a refurb so took a look at the alternator.
I'll try to post up a photo tomorrow.

No surprises that the casing has cracked (burst open) after experiencing the death squeal from the belt last winter, but luckily the crack is on the underside of the finned casing where the laminated iron core has corroded and swelled. The alternator still spins freely and charges fine so I'll do my usual ACF50 treatment and see how many years I can squeeze out of it.

 

[Bendy toy]

Mine is still making a squeaky rattle but definitely no screeching.
I had the petrol tank off today.
(1) the return fuel pipe is sitting as it should. So no further forwards there.
(2) the alternator looks fine I've poke around with a flexible inspection camera and can't see anything dodgy.
So I still haven't sourced the annoying rattle.


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