Low voltage? '83 CB650sc

[slodoug]

so on todays ride, i stopped and took a pic, then bike would not start, battery didnt have enough crank. voltmeter says 11.2 - 11.4 the whole time. Its a normal battery. water level fine. im re-newing the battery on the charger now. I tried running the STATOR COIL and ROTOR COIL CONTINUITY TESTS in the FSM but i dont think my multimeter setting was correct. Anyone do this? I ordered a new Lion battery and will test the rectifier after the battery charges.

I was able to bump start it in 1st gear.

[mollusc]

Lithium batteries aren't usually recommended for older bikes because they often have very specific charging requirements, which these regulator/rectifiers don't provide.
Nighthawk charging systems are known to be weak, and really don't put out enough current to charge the battery until you're up around at least 3k rpm.  Riding around town will often not keep you up high enough revs to charge the battery.  What type of riding were you doing?

[slodoug]

I was riding in town a lot, but had a good stretch of highway speed. the battery tested exactly what it read on the bike, 11.5v when i hooked up the charger.

I installed a Lion on my cm400a and it worked fine with a new rectifier. Most of the newer ones now have overcharge protection circuit built-into the top.

[slodoug]

according to the FSM, my rectifier is bad, it failed the ohm resistance test. stator test was fine.

[slodoug]

at 2500 rpm, i get about 12.5v if I dont have the LED lights or DVR turned on, it goes down to 11.5 if I run those.

[mollusc]

2500rpm is barely enough to keep the battery from discharging.  You should be seeing upwards of 13v.

[slodoug]

service bulletin in the FSM says 14-15v at 2500rpm. I ordered a new rectifier.

[mollusc]

I'd say that those numbers are unlikely.  New rectifier will hopefully improve things, but I would be surprised if you get that much voltage at rpms that low.

[slodoug]

changed to Lion battery and kept old regulator. that Caltric brand is crap, was only putting out 10.6v. Im going to get some contact cleaner and clean the pins. I was getting 13.5v at 3000rpm.

[slodoug]

well, bike died today. most of my ride was 3-5k in rpm and the battery did not charge, ran dead. going back to standard battery and ordered a new stator just to freshen things up.

[Larry Fine]

Replacing parts is a terrible and expensive way to troubleshoot.

The shop manuals have procedures for narrowing down the problem.

[slodoug]

true, but parts are cheap. I doubt its the rotors and my new rectifier puts out the same as the old one. When i measure the resistance on the yellow wires, it varies if they move so im hoping the new stator i get fixes it.

[slodoug]

new stator installed. 14.2v at 2k rpm without even trying.