Topic: Really stumped on charging/battery issue...CB750K7

[seanbarney41]

Try checking ohms value white to green, then disconnect green and try white to groun xd  BOTH WITH POWER OFF

white to green connected 4.5 ohms
White to ground(swingarm bolt) with green disconnected 7 ohms

[bryanj]

Isorry i misled you there you need to do those tests with the white and green disconnected under the sprocket cover, you are trying to test the resistance of the field coil and if it is shorted to ground, disconnecting green at reg still means the green at field coil is grounded elswhere.

Secondary question, is this a rebuild where the frame has been painted or coated?

[seanbarney41]

Well the arcing is pretty severe.  With the bike running, that setup is overcharging, seeing spikes up to 16 volts at around 2000

Does the field still measure 7 ohms?
The jumper bypasses the reg, turning the charging system on full. This means the field, stator, and rectifier and their associated wiring are OK.

white wire to battery negative now measures 8.6 ohms

[scottly]

white to green connected 4.5 ohms

With the white connected to the reg, you are reading the field in parallel with other loads, so the reading is lower. The green reg wire is the common green ground that runs through the harness and has branches for the reg, the rect, brake light, etc.
Go back and measure the voltage on the black reg wire, key on, not running. The white reg wire should read the same voltage.

[scottly]

[white wire to battery negative now measures 8.6 ohms

Hmm, that's weird??

[seanbarney41]

[white wire to battery negative now measures 8.6 ohms

Hmm, that's weird??

is it possible that letting the dismounted reg rest against the frame affected the reading?  Just tried it again isolated with a rag and got 7.5

[seanbarney41]

white to green connected 4.5 ohms

With the white connected to the reg, you are reading the field in parallel with other loads, so the reading is lower. The green reg wire is the common green ground that runs through the harness and has branches for the reg, the rect, brake light, etc.
Go back and measure the voltage on the black reg wire, key on, not running. The white reg wire should read the same voltage.

10.9 volts at the black wire.  Less than 1 volt at white wire...like .03, .04

[seanbarney41]

Bryan j, no this is not a repainted/powder coated bike, but it was sitting since '97.  I should probably check/ clean the upper motor mount ground connection.

[scottly]

[10.9 volts at the black wire.  Less than 1 volt at white wire...like .03, .04

That implies a bad reg. With both the black and white wires disconnected, measure the resistance between the black terminal and the white terminal; should be zero or close to zero ohms. Also, if the 10.9 volts was with 12v at the battery, you have too much resistance in the switched 12v circuit: the main fuse holder is the most likely suspect.

[seanbarney41]

All That sounds possible...gonna look into it.

[scottly]

When you go to check the voltage drop on the black wire, put one meter lead on batt + and the other lead on the black wire. This will read the amount of drop directly, instead of subtracting one voltage from the other, all while the battery voltage gets lower and lower. (Fix the reg first)

[seanbarney41]

Ok  Fixed it!   Its a real groaner.  Have to wait til I get home to tell ya.  Cell phone battery almost dead.

[scottly]

Wires on wrong reg terminals?

[seanbarney41]

Yup...

But not cause I can't match the colors that are proudly displayed on the side of the regulator cover.  I had that right.  Someone must have spun the cover around 180.  So green and black were reversed.  Soon as I switched em.  Bam.  Magnetism at the screws with the key on.  Started it up and was rewarded with nothing less than 12.8, nothing more than 14.7 at the battery.

So, one benefit of having a good supply of used spares and complete running bikes is when I started comparing regulators there are at least 2 versions, one with terminals pointing straght back towards the middle of the bike and one with terminals out the side ponting to the rear of the bike and one of them has a B as the last digit of the part number.  The layout of the electrical panel also changed over the model run too.  Anyway, something clearly got mismatched somewhere in this bikes history.

[scottly]

That was fun!!

[seanbarney41]

Glad you are not mad Scottly!  Big thanks to you and BryanJ for spending a whole day helping me with this!  You guys can console yourselves with the fact that I spent a good 6 hours swapping parts and trying to figure this out yesterday, by myself before I ever even posted.

sheesh....was startin to think I was going crazy!  Finally, my buddy dragged me away long enough to stuff a couple beers and a burger down my neck, I started digging around for regulator number 3 when all of a sudden it hit me in the face!...

[scottly]

Mad? Why would I be mad? I love this #$%*, especially when we figure it out! I made my living by trouble-shooting, a good deal of the time over the telephone. The internet makes it a whole lot easier.

[HondaMan]

Mad? Why would I be mad? I love this #$%*, especially when we figure it out! I made my living by trouble-shooting, a good deal of the time over the telephone. The internet makes it a whole lot easier.

Me, too.
'Tis such a great feeling at the end, ain't it?