Recently I rode quite a distance home in the dark and although my light is bright. It lacked a good beam effect and provided poor visibility, it was as if gravity caught hold of it at the end of the mudguard !!
Instead of a re silvered reflector, which was the issue I believe, I bought a new reflector from the Czech lads at netley marsh autojumble, which came with a nice bulb holder assy and bulbs
I fitted it today and immediately noted a much better light than before, job done i thought, but as I revved the motor, I noticed a "whirring " noise from the dynamo, I hadn't really noticed this before, so my question is
Is this whirring noise normal coming from a loaded dynamo ?
The bike has a std 45 w dynamo, good wire harness, electronic regulator, new 6v bulbs and a led rear/ brake light - dynamo re- conditioned 2 years ago
Sounds like it might be the brushs making a bit of noise as they go sliding over the spinning armature.
If you pull the inspection band off the generator, you should be able to see the level of brush wear and armature commutator condition. Also any noise emanating from this area should be louder with the cover off.
Ran out of time today to check the brushes but will do so next time
Under idle engine speed all sounds ok, but this noise appears as I wind on the throttle a bit
The light is intense so I hope it's just electrical load being placed on the dynamo
One thing I have not checked is that the correct bulb (wattage) is fitted, I know I should have checked but as it was an all complete assy,I didn't think it was necessary
Chris
Don't think it's a bearing but a good idea to check
The "short" 40Watt dynamo has a bearing only on one side,
As far as I remember.
The other side goes through a bronze bush which needs to be oiled from time to time,
To prevent friction with the armature and prevent rapid wear there.
The noise, as John Edwards mentioned, usually comes from the brushes,
But it worth to check that the bushing is oiled.
When you rev the engine over the point of the "cut out" point of the regulator,
(Mechanic or electronic) the dynamo starts to charge, and starting to build a mechanical resistance
To be turned by the engine, as it produces electricity to charge the battery and work the lights.
Usually in this point it starts to be less quiet, and it is normal.
Sometimes, if you keep the RPM steady as you hear the noise with lights on, and then shut the lights off,
The noise will decrease or go all together, as there is less mechanical stress on the system (also on the dynamo drive (timing) side)
You can try and smooth the commutator a bit with emery cloth as it turns
(and brush off the fine files from the commutator contacts) sometimes it help.
Anyway, a little bit of noise from the brushes is very normal..
I agree with Noam, if you are running the bike with a flat or battery that will not hold its charge then the dynamo is under load trying to charge the battery. Check the small bronze bearing under the cover and oil the felt pad. I have noticed thet the 40W dynamo does make more noise thn the 60W, the old 3 brush type make even more.
