Updating / Uprating a 1980s charging system
Discussion
Are there any motorbike charging system experts on here?
I'm looking to improve the charging circuit on my 1983 BMW R65 and its such a simple bike, I suspect that ways of doing this are not confined to using BMW specific parts or expertise... At present, in cold weather, it only seems to show any signs of charging the bike above 4000 revs most of the time and in spite of the good health of the battery I'm struggling to restart the bike after shorter journeys. I understand a modern system could see it charge from 2-3000 rpm.
I will also swap out the 20w50 oil for some 15w50 to make it easier to start and less drain on the battery, plus replace halogen bulbs with low draw LEDs.
At present, the bike has the standard three-phase alternator, a diode board for rectification, a voltage regulator, the GEN lamp, the battery, and the Ignition switch and a Kill switch.
I understand that I can bypass / remove the diode board and regulator and replace them with a modern regulator rectifier? Any recommendations? Are they fairly interchangeable? Many thanks!
I'm looking to improve the charging circuit on my 1983 BMW R65 and its such a simple bike, I suspect that ways of doing this are not confined to using BMW specific parts or expertise... At present, in cold weather, it only seems to show any signs of charging the bike above 4000 revs most of the time and in spite of the good health of the battery I'm struggling to restart the bike after shorter journeys. I understand a modern system could see it charge from 2-3000 rpm.
I will also swap out the 20w50 oil for some 15w50 to make it easier to start and less drain on the battery, plus replace halogen bulbs with low draw LEDs.
At present, the bike has the standard three-phase alternator, a diode board for rectification, a voltage regulator, the GEN lamp, the battery, and the Ignition switch and a Kill switch.
I understand that I can bypass / remove the diode board and regulator and replace them with a modern regulator rectifier? Any recommendations? Are they fairly interchangeable? Many thanks!
The only way I am aware of upgrading the BMW boxers charging systems is to see if you can get a hold of an old police spec alternator off an ex plod R80RT. I think they give a higher output in order to run the radio, sirens and lights.
That all said, it sounds to me like your system has some issues as, while they were never brilliant, they were always good enough to run the road bike. There was a common issue of the windings in the alternator rotor failing. That was either a complete failure (easy to spot) or a short that reduced the active windings and thus reduced the output capability.
The alternator brushes also needed to be viewed as consumable items. If you haven't then I'd suggest replacing the brushes.
Finally there was a circuit board that managed the alternator output It had 3 feeds from the different parts of the stator. one was "on all the time" to support the drain of the running engine with the second two coming in when the electrical load was enough (lights on etc.). There may be an issue with that not identifying that the system is loaded soon enough, or some of 2nd and 3rd phases not being able to deliver.
That all said, it sounds to me like your system has some issues as, while they were never brilliant, they were always good enough to run the road bike. There was a common issue of the windings in the alternator rotor failing. That was either a complete failure (easy to spot) or a short that reduced the active windings and thus reduced the output capability.
The alternator brushes also needed to be viewed as consumable items. If you haven't then I'd suggest replacing the brushes.
Finally there was a circuit board that managed the alternator output It had 3 feeds from the different parts of the stator. one was "on all the time" to support the drain of the running engine with the second two coming in when the electrical load was enough (lights on etc.). There may be an issue with that not identifying that the system is loaded soon enough, or some of 2nd and 3rd phases not being able to deliver.
Motobins and Motorworks both offer upgraded charging systems.
According to the Motorworks website:
...a cure for the small capacity original charging system! With the standard system should you wish to fit extra lighting or heated clothing this can lead to chronic undercharging and battery problems.This kit produces 600 watts of power at much lower engine speeds than before. Serious charging starts at 2000 RPM and the maximum output is achieved at 4000 RPM (which was the onset of actual battery charging in the original system!).
https://www.motorworks.co.uk/alternator-conversion...
According to the Motorworks website:
...a cure for the small capacity original charging system! With the standard system should you wish to fit extra lighting or heated clothing this can lead to chronic undercharging and battery problems.This kit produces 600 watts of power at much lower engine speeds than before. Serious charging starts at 2000 RPM and the maximum output is achieved at 4000 RPM (which was the onset of actual battery charging in the original system!).
https://www.motorworks.co.uk/alternator-conversion...
I have a 1978 R60/7 that I bought in Feb 22. It charges well enough to start the bike even when it hasn’t been used for a couple of weeks and I can run my heated jacket and gloves, and standard bulbs in the lights.
What I did have to do was clean up the contacts on the starter relay, and tighten the nut on the starter motor 12v terminal where battery lead and alternator output meet. Finding that loose nut was the turning point. Starting improved and the battery going flat on a ride became a thing of the past.
I also replaced the alternator brushes and cleaned up the slip rings on the alternator. All small jobs costing me very little money but I’m really happy with the way it works now. I did replace the original electro-mechanical regulator with a solid state one but that was probably not necessary.
What I did have to do was clean up the contacts on the starter relay, and tighten the nut on the starter motor 12v terminal where battery lead and alternator output meet. Finding that loose nut was the turning point. Starting improved and the battery going flat on a ride became a thing of the past.
I also replaced the alternator brushes and cleaned up the slip rings on the alternator. All small jobs costing me very little money but I’m really happy with the way it works now. I did replace the original electro-mechanical regulator with a solid state one but that was probably not necessary.
Is the R65 like the bigger BMW twins of old, which like Guzzis, had what amounts to a car alternator grafted on the end of the crankshaft?
These are Not Like Most Other Bikes.
Most other bikes have a permanet magnet rotor and a bunch of stator coils. This produces unregulated AC, the reg/rec either switches coils in and oout, dumps excess power or blocks excess power.
The Guzzi type, like a car, controls the current running through the rotor coil. The rotor is powered via brushes.
If you're getting through a lot of brushes, it can be a sign the crankshaft is moving about due to worn main bearings, or oil leaking from the seal.
The basic tests are:
Does the light come on and go out? If no, check brushes, rotor, wiring...
Does it raise the battery to about 14.4V at anything above tickover? If not, either the battery is very low, or you need to check the regulator, rectifier, wiring etc etc.
These charging systems are fundamentally good when working, there should be no need to upgrade unless you are running multiple cibies or something!
It's a long time since I've worked on one, I recall getting a Durite regulator from my local motor electrics shop.
The thing I do recall needing an upgrade was the fuse box, which used those horrible 'continental' fuses like a festoon bulb.
These are Not Like Most Other Bikes.
Most other bikes have a permanet magnet rotor and a bunch of stator coils. This produces unregulated AC, the reg/rec either switches coils in and oout, dumps excess power or blocks excess power.
The Guzzi type, like a car, controls the current running through the rotor coil. The rotor is powered via brushes.
If you're getting through a lot of brushes, it can be a sign the crankshaft is moving about due to worn main bearings, or oil leaking from the seal.
The basic tests are:
Does the light come on and go out? If no, check brushes, rotor, wiring...
Does it raise the battery to about 14.4V at anything above tickover? If not, either the battery is very low, or you need to check the regulator, rectifier, wiring etc etc.
These charging systems are fundamentally good when working, there should be no need to upgrade unless you are running multiple cibies or something!
It's a long time since I've worked on one, I recall getting a Durite regulator from my local motor electrics shop.
The thing I do recall needing an upgrade was the fuse box, which used those horrible 'continental' fuses like a festoon bulb.
Many great ideas and things to check, thank you. I’ve got no additional draws on the battery and the charging circuit appears to be working to some extent. I will do some more checks, find out what I’ve got already and work out the most cost effective ways of making it more efficient.
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