DIY Lucas E3L field coil rewind

[Bsareg]

Sounds like you're losing the field current. If so and if the cutout contacts remains closed, there will be a large discharge through the armature. Look for an intermittent open circuit between the F on regulator and the F on dynamo. Usually a green wire.

[Swarfcut]

BSA Service Sheet  804 gives basic testing procedures and adjustment data for Lucas MCR 1 and MCR 2 Regulator Units. The regulator bobbin contact constantly vibrates to vary the field current, so under some circumstances  small sparks will occur between the regulator contacts.

 I would suspect the cut out is sticking. Stuck open, no charge to battery, no regulator sparking, discharge on ammeter with lights on. Stuck closed, works OK, but constant discharge  at low revs, below cut in voltage, and at rest, battery discharging through dynamo windings.
   First basic check is dynamo output, and integrity of wiring loom, looking for dry joints, split insulation, short circuits. Regulator terminals, clean and tightly connected into the regulator unit. A good spray with contact cleaner recommended and a continuity check between the terminal sockets and their corresponding circuit within the regulator cover.

 Swarfy.

[trevinoz]

Kiwi, you need to service the regulator as per the service sheet.
Maybe a good idea to remove the regulator armature and fixed contact and give them a birthday with a fine oil stone.
Do all of the adjustments with feeler gauges as per instructions.
Check continuity between "D" & "F". It should be close to 0 ohms.
Push in the reg armature and you should see at least 35 ohms, usually more and sometimes infinity, depending on the state of the resistor.
Check between "D" & "A". Should show an open circuit at rest and close to 0 with the armature pushed in. These contacts are silver and should be treated with care. Maybe a light dressing.
Next you have to adjust the regulator.
I do them on the bench with a generator.
First set the voltage on the regulator then set the cut-in voltage on the cut-out.
I then connect a battery and fine set the voltage.
Note that there are different MCR2s.
The early type come as either a 60W or 45W reg.
Identified by the number of heavy turns on the regulator bobbin.
5 for 60W, 7 for 45W.
The later type have the same mechanism as the RB107 & RB108.
Good luck, the first time is the worst, it becomes easy with practice.
If you have the late type mech, you need to look at the RB107 service sheet.

[KiwiGF]

Thanks everyone, you've given me some ideas to get it working (especially Trevor). I have used the Lucas and bsa service sheets to set it up with feeler gauges etc (I did this a few years ago) but it’s got this annoyingly intermittent issue of stopping charging.

It might be just me but the service sheets say they are showing the “circuit diagram” of the regulator but I yet have to fully figure out what bits (eg coils, resistor, contacts) connect to what from the info given.

I’ve just achieved an improvement by cleaning the cut out contacts, Which I noticed will stay shut even when not conducting (eg if you put paper between them) and this stops the system charging, which is the symptoms I’ve got.

Oddly after cleaning the cut out I just went for a 15 mile ride and it stopped charging after 10 miles (according to the ammeter) but when I got home and stopped the engine, connected a voltmeter, restarted the engine and measured the battery volts it was charging again! (Also it was showing a charge on the ammeter).

The cut out contacts are ALWAYS closed when the engine is running. Open when not. I can not adjust them to open even at very low revs, but I’m assuming that is not causing the charging issue?

It’s good enough to take on the rally this weekend, and I’ll get onto fixing it next week (famous last words).

I also have a feeling the battery has a duff cell with a bit of resistance, it’s gets warm when charged by a charger, and i also suspect the ammeter is not always telling the truth! I’ll try the new 6v battery I just bought next week to rule that out as a issue. When it arrived I fitted that to my other bike (which has a dvr2) and the “old” battery in this one.

Edit: my reg has 5 turns on the reg bobbin (the pic I posted earlier by luck shows this so didn’t have go to the shed to check, it has an adjusting screw on the reg top contact, no need to bend anything to adjust it, so I guess it is a “late” 60w model)

Edit again: I’ve just found this circuit diagram and did a screenshot, it (only) makes sense to me if the “frame” is viewed as a common connection for the 5 wires connected to it (the frame sits at dynamo/armature output voltage), I also edited it where lines were “broken” (it must have been poorly scanned). It helps me to understand it if the “series” coils are just viewed as solid wires connecting “a to b” as they so thick they have very little resistance (unlike the shunt coils). The job the the series coils do (I thinkj is just relatively minor temp and battery condition compensation. The shunt coils actually close/open the 2 contact breakers.

I think the circuit diagram (probably) confirms that dodgy regulator bobbin contacts cannot (completely) prevent charging provided the resistor is ok (the F and D of the dynamo are always joined together directly, or via the resistor, but never not joined) also that if the cut out contacts close when the engine is running, then the dynamo is “flashed” ok and producing significant voltage/current, but if the cut out contacts are dodgy this can prevent the battery charging even when all else is ok.

As a test I will check if the dynamo will charge the battery with the lights off and the regulator contacts held apart with a piece of paper. This might rule out those contacts causing my issue of “no charging”.

[KiwiGF]

Kiwi, you need to service the regulator as per the service sheet.
Maybe a good idea to remove the regulator armature and fixed contact and give them a birthday with a fine oil stone.
Do all of the adjustments with feeler gauges as per instructions.
Check continuity between "D" & "F". It should be close to 0 ohms.
Push in the reg armature and you should see at least 35 ohms, usually more and sometimes infinity, depending on the state of the resistor.
Check between "D" & "A". Should show an open circuit at rest and close to 0 with the armature pushed in. These contacts are silver and should be treated with care. Maybe a light dressing.
Next you have to adjust the regulator.
I do them on the bench with a generator.
First set the voltage on the regulator then set the cut-in voltage on the cut-out.
I then connect a battery and fine set the voltage.
Note that there are different MCR2s.
The early type come as either a 60W or 45W reg.
Identified by the number of heavy turns on the regulator bobbin.
5 for 60W, 7 for 45W.
The later type have the same mechanism as the RB107 & RB108.
Good luck, the first time is the worst, it becomes easy with practice.
If you have the late type mech, you need to look at the RB107 service sheet.

On D to F measured at the dynamo 1 ohm and 47 ohms (cleaning the contacts or “wobbling” them does not affect the lower figure.

On D to A zero ohms and open circuit, measured at reg. all good there.

Now I see the resistor is 47 ohms I’m wondering if this means the dynamo will not reach 6v if the reg contacts are dodgy) I guess it’s there just to keep some current going through the field at all times to reduce sparking at the breaker? I’m off on the rally early tomorrow so further tests will have to wait.

[Bsareg]

You're now on the right lines. To clarify a little, as you say, the the 47 ohm resistor allows the field to carry some current and so prevents a lot of arcing at the regulator points when they are vibrating. The thick series wire on the cut out coil is wound in the opposite direction to the inner coil. This speeds the collapse of the magnetic pull and frees the contacts earlier. That why when closing throttle the ampmeter will show a discharge for a moment before returning to zero. Temprature compensation is provided by the spring between the brass adjusting screw and the moving part of the coil. This spring is a bi-metalic strip that will (should ) adjust the output voltage to compensate for high temeratures. Keep going you'll get there soon !!

[KiwiGF]

You're now on the right lines. To clarify a little, as you say, the the 47 ohm resistor allows the field to carry some current and so prevents a lot of arcing at the regulator points when they are vibrating. The thick series wire on the cut out coil is wound in the opposite direction to the inner coil. This speeds the collapse of the magnetic pull and frees the contacts earlier. That why when closing throttle the ampmeter will show a discharge for a moment before returning to zero. Temprature compensation is provided by the spring between the brass adjusting screw and the moving part of the coil. This spring is a bi-metalic strip that will (should ) adjust the output voltage to compensate for high temeratures. Keep going you'll get there soon !!

Thanks, yes I’m gradually getting there (finding a circuit diagram I mostly understand helps!). You’ve made me think, should the cut out points separate whilst the engine is running? Is it a major problem if they don’t? (Cos I don’t think mine do......)

[Bsareg]

The cut out points stay shut when charging. Just to clarify the cut points are the ones under the loop the regulator points are directly on top of the moving armature. If your cut out points are opening when running, it sounds like too much tension on the rear spring which is adjusted by the brass screw at the rear of main frame. Temerature increases the tension as the bi-metalic spring warms. This would make sense with your problem of charging stopping after a few miles

[Bsareg]

I should of added that accurate  adjustment of this screw is important. Though difficult without a variable power supply, what you're aiming for is the contacts to reliable close when the dynamo starts charging as the revs rise and reliable points separation when the revs drop to just above tickover. If you can get the two operations then you're  close enough. This adjustment does not effect charging voltage only cut in and out voltage.

[duTch]

 If it's any help, I found the information in this link a few years ago but from a different source (had to do some searching to find it);
 It's 1.8MB so too big to attach, so easier to download and save. I found it useful for a better understanding how MCR2 & RB107/8 work....

https://www.fromtheframeup.com/uploads/Lucas05_Generator_Output_Control.pdf] [Search domain www.fromtheframeup.com/uploads/Lucas05_Generator_Output_Control.pdf] https://www.fromtheframeup.com/uploads/Lucas05_Generator_Output_Control.pdf

 But I can attach the guide I use for doing my reg., so have done so
 

[KiwiGF]

The cut out points stay shut when charging. Just to clarify the cut points are the ones under the loop the regulator points are directly on top of the moving armature. If your cut out points are opening when running, it sounds like too much tension on the rear spring which is adjusted by the brass screw at the rear of main frame. Temerature increases the tension as the bi-metalic spring warms. This would make sense with your problem of charging stopping after a few miles

I’ve got the opposite issue (I think) ....I cant adjust the cut out points to separate at low rpm, they only separate when the engine stops completely. I guess this means “bending” something or, as my question before, is it ok to have this situation even tho it may result in the battery discharging at very low  (Not3 by very low I mean with ignition retarded, as it slightly charges on a “normal tickover

I’m also thinking I might revisit the diode idea, next week when I’m back, but this time try placing it in the feed to the ammeter (not in the field/armature circuit).

Edit: I found time to bend the cut out “stop” downwards (reducing the points gap) and the cut out points now DO separate on very slow tickover (just over 6v with lights on). On normal tickover it’s (just) charging with the lights on at circa 6.5v, whereas I’ve heard they normally discharge on tickover, that might be cos I put a few extra turns on the field coil 

[ironhead]

Just Thought I'd throw my 2 cents worth in here. I had the very same symptoms on another BSA ( B33) a while back.  Charged good with lights on for about 10-15 minutes then stopped charging. I went through all the settings etc etc . Even swapped generators - no difference. Finally gave in & fitted an electronic reg.  But when removing the bobbin assembly found a wire ( from vague memory the cutout bobbin) that was broken but still touching its terminal. I'll get back to trying to fix it properly one day but has been working faultlessly with the electronic one so far & as I use this bike every day, need lights.

[Bsareg]

Both part of the cut out points are adjustable by bending. First slacken the two screws holding the assembly together, press the armature (the moving part that carry one half the contacts ) until it lies flat on top of coil core, while holding tighten screws. This the correct position for the armature when energised. When tightning screws , make sure the two contacts line up. By bending the upper part, the upper contact should slightly bend the lower contact before it hits the core, this is to ensure good connection, there is also a slight sweep as they close to clean the surfaces. Now adjust the stop until there is a credit card thickness gap at the points when at rest. This is all rough and ready but will be within Lucas limits. Your field rewind (nice job) cannot cause battery drain on a correctly setup regulator. Athough lots of people run down MCR and RB reguators, they are more sophisticated and require more accurate assembly than many think. This scribble has taken longer to type than the job will take. Good luck 

[Bsareg]

Again I should have added, once the mechanical adjustments have been made, then check and adjust the cut in and drop out voltages and adjust using the brass screw with a spring (or locknut )  at the rear of unit.

[Guy Wilson]

all of this has reminded me I've been running on a total loss lighting system for a few years now and really should get around to fixing it.. I'm currently running with a 12 volt 7amp hour UPS battery that needs charging every month or so depending on how much light I need. The brake light is my priority...
Guy