Originally Posted by madvulc
any one ....please help how do i test my charging system...86 vn 750. ?
The problem ... ride for a while and battery slowly discharges.
Mad...I'm going to assume you've checked the obvious and/or you have an up to par battery, pref a MF or have checked the water level in the stocker. Also, a quick down and dirty test is to connect your voltmeter across the battery terms directly, and rev the engine. You should see anywhere from 12.5v ~ 12.8v DC with the engine off, 13v ~ 13.8v or more DC (gradually increasing) as you roll on the throttle. If you see that the DC voltage increases w/ rpms...that's a a good first start, esp if the voltage stays relatively constant at higher rpms.
Otherwise, grab your VOM and...
Remove the left side cover and find the stator/RR leads. They will be 3 yellow wires w/ bullet connectors that go from the stator to the RR (under the battery box if not relocated). After charging your battery FULLY, you can do 3 tests to check the stator, as well as voltage tests at the battery and resistance measurements at the RR.
Stator Coil Resistance
Set VOM to read ohms on lowest scale.
After disconnecting the bullets, check the resistance between any 2 yellow leads on the stator side....you will do 3 measurements total. All three should be roughly the same, and be in the range of 0.34 ~ 0.52 ohms. If the measurement is higher than the spec, the stator has an open winding and must be replaced. If the measurment is lower, the stator is shorted and must be replaced.
Stator Coil Isolation test
Set VOM to the highest ohms range, and test the 3 leads vs a good ground. Red lead on the yellow, black on the ground. There should be NO continuity..none, on any of the 3 readings. Any reading less than infinity means stator died and went to heaven....
If you're still in the game after these two (great!), then start the bike w/ the stator wires still disconnected (fully charged battery!).
Set you VOM to AC volts
, and check any two legs of the yellow stator wires, just as above.
You should see IDENTICAL
AC readings, varying with the throttle, ranging from maybe 13 ~15vAC at idle to possibly more than 50 vAC at 5000rpms.
If your stator does OK on these three tests...lucky you...you just may have a bad RR or a battery.
When you do these tests, remember to jiggle wires around a bit to try to locate shorts.
Do these, and let us know.
You can test the RR next...