Topic: 1979 CB650 electrical system - help please

[Barneycanoe]

Hello all,

My 1979 CB650 quit charging the battery last year. First I purchased a new regulator/rectifier, since that is usually the culprit, (replaced three on other bikes) and then realized it was actually the rotor.

Got a replacement rotor from Parts n More in Canada (I'm near Toronto), tested it, and installed it. So at 5,000 rpm I only get about 13+ volts after 30 seconds or so of revving. My wife's 1985 CB450SC does 14.5 volts at 2000 rpm.

Thought I had fried the regulator last year so bought another, same deal. Being as how the bike is 43 years old should I be looking at the stator next? I have tested the resistance and that is fine but can't figure out how to test the voltage it is putting out.

This bike is used on short trips mainly but 13 volts is not going to do the battery any good (New battery).

Also, may have to sell next year and I don't want to sell something with a problem known to me.

Thoughts and advice?

Thanks. Dave

[fizzlebottom]

The FSM has procedures to test both the stator and rotor with a multimeter. There are not many components in the charging system, and you've already replaced a few. Don't go replacing bits willy nilly though; test first, then replace as needed.

In short, get a copy of the FSM and follow the procedures it calls for.

[scottly]

Have you replaced the brushes??

[Barneycanoe]

Re-tested the Stator (hadn't since last year) and one of the yellow leads is giving nothing for resistance and the wire coating has flaked off in some places on the actual stator. I think it is the stator. Brushes look ok and ride ok on their springs.

Dave

[bryanj]

If the varnish is comming off the windings its toast and its the first one i heard off in 40yrs, if its the leads in they can be replaced

[scottly]

Brushes look ok and ride ok on their springs.

Dave

The brushes are usually the first thing to fail, and are considered wear items. I've seen them wear out in only 8000 miles on the '79 CBX. How did your rotor fail? If it had lower than normal resistance, it would have increased the current and heat through the brushes, which can soften the springs. You should measure the rotor resistance through the brushes to be sure, after you fix the broken stator wire.

[Flyin900]

The CB 650’s are know for rotor failures as a common issue on those bikes not the rectifiers. That said testing the other components is key and yes the stator should not have the epoxy coating flaking. If your measuring any of the three yellow wires shorted to ground the stator is shot.