Each component in an electrical system "sees" the world through it's connections. It only knows what it is given and with that, it manipulates it output terminals based on that info.
Therefore, if you suspect the R/R isn't doing its' job, view the world through it's "eyes" monitoring what occurs on its terminals.
We'll work "backwards" through the charging system from battery to the alternator, then back to the battery from the alternator.
First, any wiring or connectors between battery and rectifier R/W and Green connection points, should be checked for good, clean, low resistance connections. Intermittent, or terminals that are making incidental contact can wreak havoc in a vibration environment.
The rectifier:
The R/R is divided into two distinct sections, as indicated in it's abbreviation. There is a portion that rectifies the AC coming from the Alternator, turning it into DC power that the battery can use. The AC wire inputs are the yellow ones. The outputs are The Green and R/W wires. Internally, you can check the diode health using a meter with a diode test function. ( --|<|-- ) There are six diodes inside that can fail in a few ways, open (no conduction), shorted conduction regardless of probe polarity, and "mutated", where its response to input conditions is so elaborate as to be unpredictable. Fortunately, the latter is not so common. There are 14 test that can be made to the rectifier section.
The first two are an overall test using the Green and R/W wires. With the R/R disconnected from the bike, place your meter probes on those wires, for reading A _____, and then switch probe contacts and do the test again B _____.
Since the job of the rectifier is to turn alternating current to DC current, the Rectifier should only show conduction or a low meter reading with the probes oriented in one direction only. The other meter polarity should show a very high resistance if the rectifier is good.
To test each individual diode in the rectifier, requires meter placement on one of the yellow leads and the other on a green or R/W, then switching meter polarity, to repeat the test. This action will give you 12 more meter readings to write down and relay to whoever is helping diagnose your charging system health. However, for your own satisfaction, if each diode conduct in one direction only, the Rectifier should be doing it's job. While it is possible for devices like diodes to change their properties at different temperatures, it is pretty rare. But, if you want to be thorough, chuck the device in an oven, set for 70 degrees C wait a few minutes and repeat all the above tests.
The wires between the rectifier and the Stator, including any connection terminals should be checked for good, clean, low resistance connections. Intermittent, or terminals that are making incidental contact can wreak havoc in a vibration environment.
The stator:
The stator is where the yellow wires com from. There are three coils commonly connected at one end of each coil, so each coil presents one end of its coil to the outside world for power delivery. It's fairly large wire and few coils winds means that each coil has very low resistance. This is a good thing for power delivery, but measuring such low resistance requires sensitive equipment and diligent test technique. Further, you actually test two coil windings at a time, since those are the only electrical access points that are available without destructive disassembly. Fortunately, the Stator is pretty rugged in normal use. If you can read less than an ohm between any two yellow leads, and very high resistance between any yellow lead and the frame housing in which it resides, it's probably OK. Again, if you really think the stator characteristics change with temperature, chuck it in the oven and repeat the tests at a higher temperature.
The Rotor:
The 650 combines the field coil and magnetic metal into one component called the rotor. It is an electromagnet. The rotating magnet is what impresses a voltage generation in the Stator. The speed of the rotation and the strength of the magnet determines the stator power availability. The strength of the magnet is controlled by a voltage delivered to it. The higher the voltage, the stronger the magnet. The individual winding wire has an insulation coating to separate it from all the rest of the winding layers as well as the metal rotor frame. Centrifugal forces are considerable in this rotating assembly, and there forces, along with heat softening the materials can cause the wire insulation to fail its primary purpose.
The winding resistance then changes along with the strength of the alternator output. Since I don't have a known good rotor, and no Honda specification for this winding resistance is available to me, I only have anecdotal reports of "standard" resistance, which has varied from about 5 to 7 ohms.
So, the first test on the rotor would be to measure it's resistance at the rings where the brushes make contact. Then measure again where the terminals meet the regulator to verify and specify what resistance the windings have.
Again this can be checked with heat applied and even better, you can check the stability of the rotor winding resistance while the engine is hot and running with some precautions and careful wire connection scrutiny. (More about this later)
It is certainly true that the lower the rotor resistance reading, the more current and power it will draw from the battery. If the there are windings shorted within the rotor, it is also making a poorer electromagnet and reducing the power output capability of the alternator.
But, first lets move toward the "Regulator" after we have verified that the connections between the rotor and regulator are checked for good, clean, low resistance connections. Intermittent, or terminals that are making incidental contact can wreak havoc in a vibration environment.
The "Regulator":
The regulator maintains system voltage indirectly, by means of battery charge state. There is a black lead connected to the regulator which serves multiple functions. One function is to supply the regulator with the power it need to operate. another function is to provide the power that regulator distributes to the alternator rotor. And yet another important function is as a monitor of the battery charge state. The regulator make s decision on how much voltage the give the alternator rotor based on the voltage it "sees" on that Black wire terminal. If terminal indicates that the battery is undercharged, the regulator passes more voltage from that black wire on to the alternator field coil, strengthening the electromagnet and the stator output capability. (assuming rotor and interconnections are operating properly) Conversely, if the regulators black wire terminal indicates the battery is overcharged, the regulator "pinches off" voltage going to the rotor, reducing the mag field and alternator output capability.
Now you should see the importance of the black wire reporting true conditions of the battery to the regulator. Which means all the wires between the regulator and the Battery, including any connection terminals, and SWITCHES, should be checked for good, clean, low resistance connections. Intermittent, or terminals and contacts that are making incidental contact can wreak havoc in a vibration environment.
The "hot-start" problem does not separate two other factors in the scenario. Time and operating vibration. You can't make it hot without time to reach the temperature, and since the engine is heating from within, it vibrates while getting to the "hot" point of the problem.
The starter can still turn slowly, if at all, when the battery is low.
Which is why I ask for a battery voltage when the problem is first identified. If the battery is strong and the starter turns over slowly, it guides troubleshooting into another direction, away from the charging system. If time, heat, and/or vibration is diminishing charging capability, then the charging systems needs further scrutiny.
ASSUMING, that the battery voltage is actually low during hot start, there are more test that can be performed to isolate the actual cause. If all the cold testing has not revealed a smoking gun. Then you have to test when the bike is still in the failure condition. (battery voltage?)
Has the black wire voltage delivery been diminished/corrupted? (voltage reading under failure conditions)
Has the rotor resistance changed?
With the engine hot, and the regulator disconnected at the black wire terminal AND the two connections to the field coil, what is the rotor resistance at the connection wires when the engine is hot, running and revved up? (may have to bump start the bike to make this test. And since the alternator can't provide output during this test, take out the headlight fuse to reduce the drain on the battery).
Which makes me think of another test. When you have a "Hot Start" issue, does removing the headlight fuse improve starting? or no change?
Now to your questions:
I do have a question. As the R/R was reading 14.9-15v, it indicates the regulator isn't doing its job.
OR, the regulator is being lied to about the true state of the battery. When the battery was at 14.9-15v, what was the voltage between the Black and Green terminals of the regulator?
If the stator has started to 'go' as it were, and is "taking the R/R with it", will it kill a new RR if I replace this one?
Assuming you actually meant to say rotor, instead of stator, there is some risk to the R/R. Lower rotor resistance demands more current/power delivered through the regulator. It is safe to say that unless the regulator has some built in over-current protection scheme inside that inaccessible container, exceeding it's current capacity will damage it. I don't know specifically its internal design or the specific components used to handle the current flow.
But, consider this. If your slip rings are "floating" and not make strong contact, or the interconnect wires are intermittent, while the engine is operating, the rotor resistance looks higher from the regulator's perspective and it then provides >less< current in this case, and the lower current diminishes alternator output capability, which would allow the battery to reduce charge state regardless of what the regulator is telling the alternator to do. It would be like shouting at a deaf child, from the regulator's perspective.
Should I keep this one until I can be very sure of the stator's status? How do I test the stator *directly* instead of through the wiring?
I think I answered the rotor/stator testing above.
There are two schools of troubleshoot/ repair of things electrical.
One is to identify the bad component and replace it.
Another is to keep replacing parts until it works again.
It's a time/effort vs. money thing, if you don't bargain in the quest for knowledge.
Which do you have more of? What's is it that you wish to accumulate the most of?
Anyway, at this time, I don't think you've proven your regulator is "bad" yet.
Cheers,
PS. I don't have time to proofread this right now. So, I may have to edit this after I get back from errands.
