[Sidecar Bob]

I highly doubt that any epoxy suitable for potting electrical parts will be "melted" by the heat from the oil. Many, many bikes run their stators in (or at least splashed by) the oil because the oil actually helps cool the stator, which typically will run hotter than the oil in the sump.



As for reducing the output of the alternator, I don't think this would make the stator last longer. You have a 55W headlight, 30W of instrument lights, tail lights, marker lights &c. Then you turn on the turn signals and they draw another 46W or so. Add another 46W or so for the brake lights.



Your alternator is rated at 200W*. It can't produce that unless the engine is turning over at something like 2500 or 3000 RPM. At idle it produces more like 75W - with just the original electrical equipment that's not enough to power everything so the rest of the power has to come from the battery. If you are just sitting at a traffic light with your brakes on and your turn signals flashing for a couple of minutes you will probably notice the headlight dimming every time the signals flash, but that's OK because as soon as you pull away the output will go back up and your battery will recharge.



Using the starter motor (even with the headlight off) really drains the battery but as soon as the engine starts the alternator recharges it.



The power available for recharging the battery comes from difference between the power required for the lights &c and the maximum alternator output. If you reduce the alternator output (or add a lot of extra electrical loads like handlebar heaters & extra lights) there won't be enough left over to keep the battery charged and you will have to connect a charger periodically (I used to have to do this every week in the winter when I run the heaters and the extra lighting most of the time).



With the voltmeter and alternator, I have been able to observe what the electrical system is doing a bit better than most of us. I have seen the alternator supply up to 10A after a hard start in cold conditions, dropping to 5A after a few seconds and eventually to nearly zero as the battery charges. During this time the voltage usually starts off a bit under 13V and rises to 14V.



I recommend that folks with later models upgrade to GL1000/1100 stators on the rare occasions that they need to replace the stator or if the engine is apart anyway and they plan on running extra electrical accessories. Unfortunately, I don't know of a more powerful stator for the CDI models. Since



* Later models with TI have 252W alternators but the extra is used up powering the ignition system.

 

[Sidecar Bob]

I assume that what your ammeter is reading is charge to the battery, not alternator output. The alternator actually runs flat-out at all times due to the nature of the regulator. What you are seeing is the 'excess' current available to recharge the battery after using the starter & at tick-over speeds. As I suspected, it does not take long for this charging current to reach zero. If the alternator was undersized, this charge time would be significant.

The ammeter is connected in series with the main fuse so that it measures the current into and out of the battery.



There has been much discussion on this and other forums over the years about the wasted alternator output. It was done that way because it was cheaper and the Japanese didn't invent regulating the voltage that way, but at least they made them last longer a lot than the Lucas (the P.O.D.) ever could.



I am waiting for some whiz kid to come along and design a regulator that does not dump the excess to ground. Maybe something based on a three terminal regulator?

As you also point out, you have extra loads & I guess sometimes you have the machine ticking-over for lengthly periods as you have time to observe the battery voltage falling.

When I first had my GL500 with the original stator & battery I could run at typical speeds in the 80-100 Km/h range all day with loads approximating the original setup with the voltmeter reading a bit over 14V, but when I switched on the handlebar heaters (3A) plugged in the electrical anti-fog helmet shield (1.5A) and turned on the 55W sidecar headlight the voltage would drop below 13V. If I ran like that all the time (the coldest, darkest part of the winter) within a week or so the battery would start to have trouble starting the engine. In those days I typically charged the battery every week in Jan & Feb and at least once per month the rest of the winter.



When I changed to the lawn tractor battery the frequency of charging became lower and when I put in a GL1000 stator it became even less, but I still had to keep an eye on things.



I never ran the 650 with a bike battery in the winter, but with the lawn tractor battery and the original stator it needed charging about as often as the 500 with its original stator and a similar battery and changing to a GL1100 stator yielded similar improvement. Last year I finished converting the 650 to HID headlights and LEDs for all other lights so I anticipate needing to charge it even less often (I was unable to find out this year because I was recovering from tendon transfer surgery in my thumb and unable to drive (or go to work) from mid January to mid April).

My own use is very light compared to yours as we don't have any significant trafic on the 'B' roads (that's one step up from goat tracks) we normally use on ride-outs. We don't often stop for more than a few seconds at junctions & the motor is normally running at 3000+ rpm. Most of us here are not brave enough to go out when it's dark. I would suggest that you & I are at the extreme ends of the current demand spectrum.

Not as much as you might think. My bikes are primarily used for commuting, the GW for summer and the 650 for winter, both pulling sidecars. Unless it has rained I usually take the (dirt & gravel) concession roads and in my 20-25 minute drive to work I sometimes see as few as 5 other vehicles on the road.

 

[Sidecar Bob]

To return to the basic question, why do the stators fail? I have several where only one coil is black & has clearly failed. I would guess this one coil has a joint in it. Or if not a joint then maybe the wires have chafed due to the wire having a slight ability to move, especially when expanded due to high temperatures.

I really don't see heat from the engine as much of a contributor. Go to any bike forum and you will see that the particular make/model they cater to there has stator problems and they were designed poorly and so on. Most of these groups are discussing bikes as old as ours. How many 25+ year old cars do you know that still have their original alternators? (The same could be said about water pump failures BTW)



In the case of these bikes, one of the biggest contributors seems to be the electrical connector. From what I can figure out, when the terminals inside the connector corrode the connections become resistive. Voltage then develops across the resistance (series voltage divider principle) and, since you now have current passing through the connection and voltage across it, power has to be dissipated and the terminal heats up, causing the resistance to increase, the power to increase and eventually the connector to melt. During this process, the connection becomes intermittent and every time the connection breaks and then makes again the current surges. If the connection is constantly breaking and making the surge current, which is much higher than the normal maximum, can damage the coil.



I also believe that many stators are damaged because of use with a batteries that have not been maintained properly and are not able to not able to charge properly.

Thanks for mentioning there is an even higher-output stator available. Does the standard regulator cope with this output? Do you have one fitted? How hot does the reg get?

I haven't measured the temperature of the reg/rec, but I'm sure it isn't an issue. As far as I can tell it is the same as the one used on the GL1100 except for the wires.

 

[Sidecar Bob]

I used a used GL1100 stator that I bought for under $20 on eBay in my 650. I replaced the original wires with nice long lengths of cloth covered #12 "fixture wire" (the stuff made to withstand the high temps inside light fixtures). #12 is a little heavier than the original (a good thing) but it is also a bit stiffer and harder to work with. The bracket that holds the wires should be replaced with the one from the original stator. I remember drilling out one hole in the armature but I can't remember why. It will be obvious when you look at them side by side. This was the second one I did and I took pics, but they were on the computer that crashed and I would have to dig through a folder of several thousand recovered jpegs to find them and I don't have the time right now. I potted all of the connections in epoxy to insulate them and prevent vibration from breaking them.