Motorcycle Repair: 73 honda cb450 charging

Question
Hi  I have 73 honda cb450 that isn't charging.  I checked at the plug coming from the stator.  None of the wires are grounded to the engine and all three have continuity between them.  I checked ac volts on all three at an idle with a multi meter set on the lowest setting of 10.  All three just moved the needle off of zero so not much.  Is my stator bad or is the magnet weak?  Thanks

Answer
Ryan, are you measuring the AC volts to ground or to each of the legs? If the stator coils are not grounded to the frame/engine and all are connected, try testing the voltage between the legs of the stator, not to ground. Test with the plug disconnected from the harness

You should be able to stick a decent sized wrench on the rotor and have it stick there. The 350-450s have similar charging systems with a current limiter mounted beneath the battery box. Sometimes those fail, grounding out much of the charging output. Disconnect the current limiter wiring and see if the power output increases back to normal again.

Rectifiers are the other common failure item. The rectifier is just a stack of diodes collecting the positive half of the sine wave and feeding it to the battery. You can test rectifiers by grounding one lead to the rectifier ground post, then testing the "hot" leads. Write down the readings, the swap the test leads and test again. You should see continuity in one direction and very high readings with the opposite polarity of the test leads.

Plug the stator back into the harness and then test for power up at the rectifier wiring. Make sure that the rectifier is properly grounded. A 12v test light will tell you a lot about what is going on, if you probe the various wires with power on and engine running.

Bill Silver