Topic: CHARGING PROBLEMS.....Need help.

[yourpiercer]

I recently purchased a 1980 Honda cb650, 10,000 miles, pretty well maintained but need a little TLC.
I did all the things you would do when buying an older bike, wires, plugs, battery, air and oil filter change and oil change of course.  The bike RUNS great when it is running......the problem is now I have charging issues....which I here is common with this motorcycle.  I got my new battery charged up and installed and the bike pops off like a champion but after riding around for a hour or so I stopped for gas and the bike barely wanted to turn over like the battery was dying.  A little more riding and I got the bike home and shut if off to take off my gear and I went back to the bike to try to start it and NOTHING!  DEAD BATTERY!  I charged up the battery overnight and put it back in the bike and started it......it started just fine. I hooked up my ohm meter to the bike and at first with high idle it was saying 14.5 ish at the battery.  I let it warm up for a minute or two and put the meter back on and it was saying 13 ish and dropping.  My guess is the stator\alternator would be the culprit??  RIGHT???   Does anyone out there know a way of testing the stator\alternator to see if that is the problem???
What about testing the rotor???  Is there a test to see if that is what is bad??
If anyone would have some advice I would be in debt to you forever.......

Thank you,
yourpiercer

[dusterdude]

hang on dude,two tired should arrive anytime now.

[Tower]

There are several posts on this topic.  Search "650 Rotor Testing"

[Ibsen]

Stator test:

LINK

Voltage regulator/rectifier test:

LINK

And take off the generator cover and Check the carbon brushes for the rotor. They have got a service limit line on them that indicates when they are worn to the point were they need to be replaced.
Then measure the resistance between the two rotor slip rings (they should be cleaned properly first), it should be more than 2 ohms, 4~6 ohms seems to be the ideal. Under 2 ohms and there are probably a short in the rotor. If the resistance is too high you have broken windings. In either case the rotor needs to be replaced.

[TwoTired]

The alternator needs a magnetic field to produce electrical power.
On the 650, that field coil is the rotor and is fed power via two brushes on slip rings.
The brushes could be worn/ and or the slip ring surface could be glazed with an insulating film.  So, clean the slip ring surface with a fine abrasive and make surw there is enough brush material left to provide good contact.

Then measure the field coil resistance.  (You could actually begin at this point, too.) I don't have specs here, but I think it is about 6.8 ohms, plus minus 10%.  If you get significantly lower numbers, the coil draws more power than the regulator can supply, causing damage to that unit as well.  Higher resistance numbers an you should then the slip ring/brushes noted above.

If your resistances check properly all the way to the disconnected regulator terminals, turn on the ignition and measure the voltage that the regulator provides the alternator rotor.  With the motor stopped, it should be very close to the battery voltage.  If not, check the voltage going TO the regulator for battery voltage.  Voltage in and no voltage out = a bad regulator.

Cheers,