Alternator Brushes - Anyone relaced them

[BillN]

R100GS - Gen light dims and never goes completely out - possibly Alternator Bushes need replacing - will have a look tomorrow

Has anyone replaced the Brushes recently - is it a soldering job

Appreciate any comments

 

[Steptoe]

- is it a soldering job

Appreciate any comments

Yes - with a good soldering gun.

Or solder some suitable sized "O" rings onto the ends of the brush wire and bolt them in place.

 

[Setzer]

Did this job myself a few years ago and as mentioned it is a soldering job but Steptoe's idea of the "O" rings is a good one, I never thought of doing that! it would certainly make the hardest part of the job a huge bit easier.

Its a bit fiddly but not too bad a job to do yourself.

 

[Rob Farmer]

I had a similar thing that turned out to be a build up of carbon from the bushes shorting out the windings. A quick scrub with a stiff brush got it back as it should be.

 

[Myke Rocks]

Generator light dims

Having worked on an airhead generator in the last week, they are fresh in my head, and I can suggest the following:
If the light fails to come on at all, it is usually brushes or an open circuit rotor. (In our case, Rotor was open circuit. OK= circa 3 ohms across sliprings)

As previous correspondent suggested, clean round brushes & check they are free.

Usually an alternator light glowing dull when running is indicative of a diode down on rectifier board. If the rectifier board is removed from the bike, individual diodes may be easily tested with a meter which has a diode test facility.
Just put probes of meter acoss individual diodes. Meter should read in one direction only, so if you swap leads reading appears or disappears.
Thus, if you do this to all, I think, - 9 diodes on the board, you can say for certain that it is or is not a diode board fault.
In my case, I was able, with confidence, to tell my friend that the diode board was definitely not faulty.
Myke

 

[John Roberts]

Having worked on an airhead generator in the last week, they are fresh in my head, and I can suggest the following:
If the light fails to come on at all, it is usually brushes or an open circuit rotor. (In our case, Rotor was open circuit. OK= circa 3 ohms across sliprings)

As previous correspondent suggested, clean round brushes & check they are free.

Usually an alternator light glowing dull when running is indicative of a diode down on rectifier board. If the rectifier board is removed from the bike, individual diodes may be easily tested with a meter which has a diode test facility.
Just put probes of meter acoss individual diodes. Meter should read in one direction only, so if you swap leads reading appears or disappears.
Thus, if you do this to all, I think, - 9 diodes on the board, you can say for certain that it is or is not a diode board fault.
In my case, I was able, with confidence, to tell my friend that the diode board was definitely not faulty.
Myke

Hi, Myke,

I fitted an increased output alternator from Moto Bins/ MotorWorks (sorry, I can't remember which) and just popped out for a look at the original alternator off my '82 RS and can confirm the reading across the slip rings are 3 ohms (NOT 'open circuit'- that's infinity ohms) Also there are a total of eleven diodes on my board- the six biggies, and five smaller ones, two of which are tucked at the sides of the space between the two boards and which I missed initially.

BillN- have you checked the field windings? there are three seperate windings (producing three phases which are rectified by the Diode Board) One of those could be shorting to Earth like mine after I trapped one of the wires of the winding while reassembling the alternator Nah, nobody else would be that daft, would they? The resistance of the individual windings should be very low, rather less than an Ohm, and I don't know if your MultiMeter would read that low reliably. Mine doesn't. On the other hand one could be broken, you could check for that by disconnecting/unsoldering the commoning point of the three field windings and checking for continuity of each.

I hope that makes sense, I'm not sure that it does, but what I'm getting at is if you are still stuck for a solution, let me know and I can lend you my stator (that's the thing with the field windings) Come to that I've got a rotor and Diode board as well, all in good order, I upgraded because I needed extra output rather than because the original was faulty.

 

[BillN]

Thanks All

I cleaned the area around and brushes with an air line and stuff similar to thinners, (but not as strong)

Marginal improvement, but the light was still on, (dull), when running

Replaced the diode board and we are back to normal - well almost

The light is on when you switch the ignition on - goes out on start up - the Bike is "ticking over" at 1100 rpm - and the light NEVER comes on to indicate that the system has stopped charging.........OK I need to get the revs down to say 900 rpm on tick over, but I have "done" for today....so it's a job for another day

I am not sure if the voltage regulator is standard........and the PO seems to have fitted a few other "bits" with the relays etc.........

 

[Myke Rocks]

Charging light

Thanks All

I cleaned the area around and brushes with an air line and stuff similar to thinners, (but not as strong)

Marginal improvement, but the light was still on, (dull), when running

Replaced the diode board and we are back to normal - well almost

The light is on when you switch the ignition on - goes out on start up - the Bike is "ticking over" at 1100 rpm - and the light NEVER comes on to indicate that the system has stopped charging.........OK I need to get the revs down to say 900 rpm on tick over, but I have "done" for today....so it's a job for another day

I am not sure if the voltage regulator is standard........and the PO seems to have fitted a few other "bits" with the relays etc.........

Easy to check.
With the engine running, either just turn off the run switch on handlebar, or stall the engine. If light comes on, all is correct.
These bikes normally charge at a tickover.
Myke

 

[Roger Chatterton]

The original Voltage Reg has a red top, the higher output one is black ; I know this 'cos just recently fitted the MotoBins high output one.

 

[Steptoe]

The original Voltage Reg has a red top, the higher output one is black ; I know this 'cos just recently fitted the MotoBins high output one.

What you really want is an old mechanical regulator. The voltage can be adjusted, and they can be repaired.

Ideal for those trips to far away places, instead of unrepairable bling.

 

[BillN]

What you really want is an old mechanical regulator. The voltage can be adjusted, and they can be repaired.

Ideal for those trips to far away places, instead of unrepairable bling.

I think that Mworks still sell them

 

[BillN]

Easy to check.
These bikes normally charge at a tickover.
Myke

Are you sure?

I thought that they normally start charging, (i.e. light goes out), at above 750 rpm

 

[Steptoe]

Are you sure?

I thought that they normally start charging, (i.e. light goes out), at above 750 rpm

Gen light goes out - they charge.

But the light going out varies enormously from bike to bike, some go out at 750 rpm, others at 1200 ish rpm.

 

[Myke Rocks]

charging point.

Are you sure?

I thought that they normally start charging, (i.e. light goes out), at above 750 rpm

What is tickover level?
I only worked on them with cold engines & choke on, so I presumed level was greater than 750 rpm.
Myke

 

[BillN]

Gen light goes out - they charge.

But the light going out varies enormously from bike to bike, some go out at 750 rpm, others at 1200 ish rpm.

But if the light does not go out AT ALL at any revs..............i.e. just before it stalls..........at say 650 rpm..............is there a problem

Light is on when ignition is switched on

 

[skywalker]

It comes on when you switch on and goes out above tickover. Easiest way to check is switch the lights on ,let it tickover then rev it - lights should get brighter.
Used to be a problem around the late 80's when the diode boards were fixed to the front cover directly instead of the older rubber mounted bushes as on early bikes. There was paint on the top mounting posts which didn't allow the unit to earth correctly, mod was to scrap off the paint.
On the earlier rubber mounts make sure the brown earth wires are on the top section of the diode board, seen them fitted to the bottom section before which is permanent live.
If you disconnect the regulator plug and look on the bottom of the regulator you will see som letters -B+ ,B- and BF If you bridge B+ and BF on the corresponding pins on the plug from the harness with a split pin,switch on ,gen light will be on . Start the bike and the light will go out and charge at about 15 -16 volts.
9 times outta 10 though faults usually the rotor

 

[uncle dick]

If the warning light stays on slightly it might just be due to voltage drop between the alternator and the instrument panel area. Very common on K series bikes and no-one worries about it.

Dick