Square Four 1955 onwards - Dynamo removal and inspection

[robert.clark]

Hi
My dynamo is in need of an overhaul as there's no charge.
I would like to inspect clean / replace the brushes first of all, but I cannot see anyway of removing the chrome end cover without removing the primary chaincase to gain access. Am I missing something here? Drags charging notes suggest its possible but can't see how.

Secondly removal of the complete dynamo in situ. Other than taking the timing case off and removing the chain drive nut and freeing the sprocket off the dynamo shaft, removing the dynamo securing strap, releasing and pulling the dynamo across to the primary side, which I see as the only other option.

Anyone out there had similar issues on this one.

[Roger Gwynn]

Awkward but possible with a bit of a wiggle.
I don't really understand your 2nd question, removing the dynamo in situ - if you remove it, as you describe it will no longer be in situ and you have described just what you have to do to remove it, so what is the question?

[will_curry]

It's possible to inspect the brushes by just removing the end cover
but to change them you will need to remove the dynamo using the
method you describe. While the dynamo is off the engine take
the opportunity to check and lubricate the armature bearings.
Also see what state the timing chain and its tensioner are in.

Are you sure it's the dynamo that's the reason for no charge?

[paul.jameson]

If you do remove the dynamo completely, make sure that you retain the dynamo sprocket in the same position in the chain. I use a piece of wire through the links to achieve this. That way, provided that you don't take the distributor out, you can maintain the ignition timing. If you do need to take the dynamo out completely, taking the carb off first makes things a lot easier.
Having taken the dynamo off completely, replacing it with a Bennet Longman alternator is a very sound move.

[robert.clark]

To clarify, in-situ means the bike is complete not already dismantled. So just trying to do what I can without removing the dynamo.
Changes well I just fitted an DVR2 electronic regulator kit, should have run the bike up first with the original regulator fitted but didn't as it did work.

Ive treble checked the regulator wiring which is consistent with others I have fitted to my other bikes. That is 6 volt conversion, positive earth.
So from the DVR2 wires to the wiring harness
F - green to green,
A - brown and white to purple ( on the Drags harness for 6 volt operation)
D - yellow to yellow fuse fitted
E - red to black
Black wire - taped off.

So I'm still working the issues
I need to rig up a bulb across the dynamo output and earth to confirm there's absolutely no output.

The Bennet Longman upgrade Ive just looked at and makes sense and probably close to a dynamo refurb cost. I would need to upgrade to 12 Volt from what I see but don't ride at night anyway.
Good advise on the dynamo removal and ignition timing. Not sure if I can escape retiming if I go the Bennet route as they use donor part from the existing dynamo to help costs.

Timing side chain and tensioner were all replaced with new at the last strip.

Will a total loss system (no dynamo charge) , ignition only, last for 40 miles to an event? I have 2 x 6 volt batteries in series. I'm considering buying 2 more batteries to carry with me.

[will_curry]

If the bike's not been started for a while there is a chance that the dynamo may
need 'flashing' to wake it up. This seems to be more of a problem when the
dynamo is working with an electronic regulator rather than the original mechanical
device.

It's all to do with decaying remanemce and transistor switching losses.

[robert.clark]

Will, I have carried out the flashing / repolarization treatment as you suggested.

Fired up and now I am a little confused on what I am seeing.

Get the engine revs right and I am showing zero on the ammeter. Above or below that and the ammeter is oscillating between charge and discharge

First of all I am going to get the batteries fully charged to ensure that issue is clear.

Second I need to take readings of what is coming out of the dynamo.

[robert.clark]

Update. The flashing of the dynamo worked and getting 6.75 Volts output was looking for 7.2 volts but that'll do for me.

Thanks for all the suggestions.