Author Topic: 1980 CB650 Custom Electrical/Regulator problems  (Read 769 times)

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Offline ABikeNamedTrouble

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1980 CB650 Custom Electrical/Regulator problems
« on: June 08, 2011, 03:43:32 PM »
Hey folks,

I imagine the answer to this question will be "you need a new rotor" but before I bite that bullet, I'd like to get a few more opinions.  Anyway, here's the situation:

I just got my 1980 CB650 Custom back it good order (full top-end rebuild, carb restoration & tune, etc.) and I've discovered a weird electrical issue.  My battery is brand new, reads ~11.8 V at idle, ~13.5 at 3000 RPM and tops out at ~14.5 at 4500 RPM or above.  So, from that, I assumed my charging/regulating system was fine.

But then I stalled out (my fault; I'm a bit of a noob rider) starting uphill and when I tried to restart it my battery was completely dead.  After jumping the bike from my girlfriend's car and recharging the battery, everything seems fine again.

I would dismiss it as a fluke, but I also noticed that the yellow-bundle connector between my R/R and wire harness is melted together, and I can't seem to get consistent readings with a multimeter from the yellow leads to ground.

Any idea what might cause this?  The PO mentioned he had replaced the R/R once and had it go bad again, but during the rebuild I attributed that to a cracked ignition coil (figuring the short was frying the R/R).  But now I'm stumped...

- Adam

1980 CB650c Custom
Keihin PD mechanical carbs
Stock air box and 4-4 exhaust
http://forums.sohc4.net/index.php?topic=97504.0

Offline TwoTired

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Re: 1980 CB650 Custom Electrical/Regulator problems
« Reply #1 on: June 08, 2011, 11:06:50 PM »
If it were me, the first thing I would do is get an accurate resistance reading across the slip rings of the rotor.  Or, at least, the wires the go to it disconnected from the R/R.  Something in the range of 4.5 to 6.5Ω would put me at ease. (after subtracting out meter lead resistance)

Cheers,
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.