Topic: cb550/650 charging system wiring woes

[paulages]

i'm wiring a cb550F with a '79 cb650 engine, and having problems with the charging system. the cb550 has a separate regulator and rectifier, and the '79-'80 has a reg/rec as a unit. as far as i can tell, the only differences in the wiring itself lies in the color of one of the wires going to the field coil on the stator. on the 550 it is green, and on the 650 it is black.
the 550:

the 650 (i colored the green wire for clarification a little bit, as it was dull in the original):


i wired up the 550 harness as follows: all yellows and whites from the 650 stator to yellows and white on the reg/rec; the red and white on regulator to the same color on the 550 harness, which goes to the starter magnetic switch; the black from the field coil (the one that's green on the 550) to one of the black positions on the 650 reg/rec; and the other black on the 650 reg/rec to the black wire on the 550 harness that was connected to the regulator on the 550. so, there are two black wires coming from the unit. i tried them in either position, and they both result in the hot (black) circuit on the bike being grounded.

am i doing something wrong, or is there something incompatible here? i tried to test the 650 reg/rec as per the ohm tests in the manual, but get NO reading through it between any wires.
 

[HondaMan]

The 650 reg/rec should have a connection between the white and black wires (the black with the tip of the arrow drawn on it, as shown on your 650 pix) as 0 ohms. Then, if you connect 0 volts to the wire you colored in as green (that's the GROUND), and also apply 14.0-16.0 volts to the black wire (3rd from the top in your pix), the white-black circuit mentioned above should open, which will result in either an open circuit or (if a resistor is used inside) a resistance of 3-10 ohms (I don't know exactly which resistor value is used in the 650, sorry...). This action will tell you that the regulator portion of the reg/rec is working OK.

Now comes the harder part: disconnect all the wires and check the rectifier in the Reg/rec. If one or more of those diodes inside is shorted, this can create a short to ground. To check it:
1. connect the RED lead of your ohmmeter to the terminal you painted GREEN. Then, connect the BLACK meter lead to each of those YELLOW wires, in turn, to see if you get a reading. It should show some resistance, not an open circuit (if you have a DIODE CHECK meter setting, use that: if you have a conventional meter, use the lowest R scale). Now, reverse the meter leads (BLACK to the green-painted wire) and test again: all circuits should act like an open circuit.
2. Check the other half of the bridge: connect the RED meter lead to the BLACK reg/rec terminal (3rd from the top in the pix), and test each YELLOW wire with the BLACK meter lead. All should show open circuits. Reverse the meter lead connections and repeat: all should act like diodes, with some resistance showing.

If any of the above tests fail, the reg/rec is toast.

The alternator: check yellow-to-yellow, all 3 combinations. All should show a low ohms reading, nearly a short, regardless of meter RED or BLACK leads. Likewise, the BLACK and WHITE wire from the alternator should show a low-resistance reading. Connect one meter lead to the case of the alternator (either lead is fine) and check between each of the wires and the case. There should be an open circuit, infinite resistance. If you get a reading here, the insulation on the stator of the alternator is damaged somewhere and it has shorted itself out.

That's about all there is to these systems: pretty simple units...

[paulages]

thanks, mark! i think i'll go grab my multimeter and the reg/rec and bring it home so i can do those tests in front of the computer. one thing though: it's unclear which black wire is which on the unit itself, as they wires are not actually arranged as in the picture. i could have known based on the connectors coming from the unit, but i removed them all to adapt to the 550 harness. also- like i said, when i tested before between the wires specified in the manual i got infinite resistance everywhere.

i'll be back soon with more info...

[paulages]

by the way-- did i mention that the original problem was that the entire black circuit on the bike was showing as 0 ohms to ground? i traced it back to the reg/rec and found that the black wires on the reg/rec were grounding somewhere. decided to switch out the 550 stuff to the 650, so that the charging system would be all 650. don't know if this is relevant. from what you're telling me, it seems like maybe the black or white wire is grounding to the alternator case. we'll see soon...

[paulages]

ok, well i found one problem. one of the wires going to the brushes (the black wire) was split on the back of the brush, breaking the continuity altogether. i replaced the brushes and holder and tested all of the alternator components to be within specs.

the regulator/rectifier on the other hand...  i get 0 ohms (more or less) between the two black wires, but infinite beween any other wires. none of them seem to be acting like diodes, unless my multimeter is malfunctioning. the manual states that the resistance should be 5-40 ohms in one direction and 2000 or more in the other. to further confuse me though, i tested several other rectifiers (cb750) i had on hand, and i get the same readings on all of them.

i have a chilton manual that refers to all the small fours together, and all the tests list as common for the other fours, and unique for the 650. they list both voltage (using battery current) tests and ohmage (using a multimeter) tests for the 500/550 rectifier, but refer specifically to just an ohmage test on the 650. because of this, i don't know if there's any reason not to do a continuity test through the rectifier off battery current.

oh well, i'll have to reserve the rest of my confusion for tomorrow...

[HondaMan]

The black-to-black reading sounds right: it should be a short when the regulator is OFF.

[paulages]

The black-to-black reading sounds right: it should be a short when the regulator is OFF.

i think the original problem was in assuming that the green wire going to the brushes on the 550 is the same as the black wire going to the brushes on the 650 (it's actually blue on my alternator, but whatever). on the 550 harness, this wire joins with several other greens between the first couple connectors at the electrical panel, which are of course a ground. if the black wires are a short on the 650 reg/rec, then this creates the ground problem i was having in the bike's black circuit. so using the 650 reg.rec, i bypassed the stock connectors and just ran that black (blue) wire straight to the reg/rec-- ground problem solved.

HOWEVER, i still don't know if the reg/rec works, as it reads as an open circuit in all directions. i'll try a test lamp through it today.