[Geirskogul]

I think that's the compressor kicking in, and it's on a belt.
 when it goes on there is more mechanical resistance.
with the stator and magnet,there is no physical connection.

YES there is a physical resistance.  When you turn any electric item on in a car, it increases load on the alternator.  An alternator works essentially like a reverse electromagnet.  In an electromagnet, a wire wound around an iron object is given a charge with electricity, and the iron rod/item becomes magnetized.  In an alternator (nutshell version) it's the opposite of that: the iron "object" is spun around inside the coils, and the coils PRODUCE electricity.   When you move similar poled magnets near each other, they repel.  That spinning iron core will repel the coils more when there is a load put on them than when there is none, so turning on something like a headlight on a motorcycle (or the headlights on an older car, 5A each at 12v) can more than double the spinning resistance.  The smaller the alternator the more the resistance is raised.

That's why, in performance and hypermiling cars, people switch "off" the alternator to increase horsepower, because the alternator causes resistance to the system when it's producing power.  To switch "off" the alternator they simply have a switch that disconnects it - removing the load on the alternator removes the load on the spinning serpentine system.  Man if it didn't produce any load on the system then it would be free energy. 

I know this isn't a car forum, but I didn't want you to have the wrong idea.  Just trying to help out

This is for automobiles, but can also be read for more info: http://www.svapowerproducts.com/html/how_much_hp_does_an_alternator.html

A bad alternator could start to make noise if one of the coils is shorted/stator is damaged/so on and so forth but not make noise without a lot of draw.  The history of the RE motorcycle points to something other than the alternator internally, like it rubbing on part of the frame, but it always COULD be the alternator itself.

[cyrusb]

Is it still apart? If so, and in fact nothing was found loose, I'd run it with the cover off and have a "look" at the noise. Just for the hell of it. Then button it up, if its not broke....

[bruce]

Thanks, everybody for all the advice.

Thanks Cyrsub: This is a really good idea. The problem is that I've just put the whole thing back together. I'll do it sometime in the future - next time I check the chain tension.

Thanks Geirhogul: Obviously you're right, you can't get energy for nothing so there's bound to be some extra work from the alternator. Since, to the best of my knowledge, magnetic flux doesn't make a noise, the thing that's probably complaining is the alternator bearing. Am I right? Does anybody know anything about the bearing system? Could it be short of lubrication or have I simply got a noisy bearing? I'm inclined to the second view. The bike has now done around 10,000 km and the noise hasn't increased - at least not much.

Thanks again.


Bruce.

[geoffbaker]

Thanks, everybody for all the advice.

Thanks Cyrsub: This is a really good idea. The problem is that I've just put the whole thing back together. I'll do it sometime in the future - next time I check the chain tension.

Thanks Geirhogul: Obviously you're right, you can't get energy for nothing so there's bound to be some extra work from the alternator. Since, to the best of my knowledge, magnetic flux doesn't make a noise, the thing that's probably complaining is the alternator bearing. Am I right? Does anybody know anything about the bearing system? Could it be short of lubrication or have I simply got a noisy bearing? I'm inclined to the second view. The bike has now done around 10,000 km and the noise hasn't increased - at least not much.

Thanks again.


Bruce.

In an earlier post you said everything LOOKED allright as far as clearances. I would suggest you really need to set the clearance between stator and rotor, and it is very easy; all you need it to remove the outer stator, wrap a length of milk carton around ithe inner rotor and replace the alternator stator around the rotor and tighten; it should then be set to the correct clearance all around. You can check with non-metallic shims.

Secondly I would look at the wires and the alternator itself. Mine had some rough edges on some of the epoxy 'potting' that could easily rub other parts.

Also, Bruce, if your setup is the same as mine used to be  (2000 500cc) then there is NO alternator bearing. The alternator is static, bolted to the chaincase. The rotor is mounted on the crankshaft and spins inside the alternator armature; so the only bearing would be the main crank bearing. And if that's making noise, you have REAL trouble... but relax, it isn't. I cannot imagine the main crank bearing making noise ONLY when the headlight is on...

I'm still thinking something is loose or out of alignment.

[baird4444]

AGAIN...   my thoughts are primary chain noise.
Is chain tension correct?
 What is your fill level? 
 Are you fill'n up to the plug or you do'n the over fill to protekt your sprague??

try adding another 1/2 Qt. of what ever you put in the primary and see if
the noise changes or goes away...
           - Mike

[bruce]

Dear All,

Thanks a lot everybody for your thoughts. I'll strip it down again sometime in the future when I've more free time.

Tip from me if anybody's interested. The problem of mayo in the oil can be cured by two changes:

i. get rid of the breather system and have a short breather venting over the chain;

ii. leave the dipstick OUT for a couple of hours at the end of a good run - lets all the water evaporate away. Best tip I ever received so I'm passing it on.

Thanks again.

Bruce.

[baird4444]

Bruce- for some unknown  reason some flys and gnats are drawn to oil. Have you ever found them stuck to a run down the side of an oil bottle or in a funnel that you used for oil or tranny fluid?  I'd hate to think that they might find their way into the oil reservoir where they may clog passages or even get flushed into a bearing or bush.
       just thinking outloud...  Mike

[petefletcher]

Bruce,
I agree about ditching the stock breather system but what comes out of the breather is mostly water and will be pretty acidic.
Do you really want that on your chain?
I vent to beneath the rear footrest but clear of the chain.

[bruce]

Dear Mike,

The guy I got the tip off was also concerned about insects. He modified a tea strainer to put in the hole when the dip isn't there.

Bruce.