Topic: 750a electrical prob

[stinkfinger]

The bike- a 1978 cb750A thats been brought back to life for about 2 years,  from when
it was parked and left for dead in 1985.
Its never given me a lick of an even the slightest electrical problem, and still even has the original
working bulbs in it.............until today.
Today I hooked up my new carb synch gauges and when i went to start it, it just
turned off all power. Ive wiggled every wire,checked the battery(12.8v) and fuses(good)
The only thing i get outta the old girl is,  when the key is turned on, after a cpl seconds it "very faintly"
lights the oil and neutral light, and slowly goes back out after a few more seconds.
Any ideas or suggestions would be greatly appreciated as i really hate tryin to diagnose
electrical probs. Its my achilles heel.

Thanx
Tony

[chickenman_26]

Tony,
BTDT. Keep that volt meter attached to the battery, and look at it after you turn the key on.  The old style flooded batteries, especially in that size, sometimes suffer what's been called Sudden Death. A tie bar inside the battery develops a hairline crack that opens up when a load is applied, causing the voltage to drop to almost nothing. After the load is removed (key off), the connection cools, the crack closes up again, and the voltage appears normal. I once had a bike towed 200 miles because of this, because the symptom just didn't make sense to me. I was convinced the almost new battery was okay. Not.

Stu

[salukispeed]

I also Had the same issue with a Goldwing battery few years back. Other things to look at, Battery cable cleanlieness at both ends. turn your key on and check battery voltage at the terminals and then from the frame to the starter relay/solenoid. Should get the same numbers both ways.
 MY 77A had the ignition switch come unplugged part way and this caused problems too. Douple check the main fuse terminals as they can get oxidized and make poor connection that can come or go, also check where the fuse box plugs in to the harness ( behind fuse box )
Just some ideas.

[stinkfinger]

You guys pegged it. It was the battery.
Threw up voltage readings all across the board.
The kid at autozone threw it on the tester and it came back
as   10.8 volts - 0 charge - needs charge     I thought maybe it wld come back as
"wont take load"  or  "bad battery" or sumthin, but no, just   "needs charge"
and the kid asked me if i wanted it charged , no thanks, tried that
Got a new napa battery, on sale for $49.99, at the local Napa.
I noticed when i took out the old battery that a cpl cells were an inch(approx) low or so,
perhaps I hastened the death of this battery a bit.
Thanx again guys,
Tony

[raymond10078]

After you put the new battery in - do yourself (and your battery) a favor and check the system voltage with the bike running - and above 3,000 RPM or so.