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| *Vultures Knob>>>Bike Lights |
1975 Honda XL250 motorcycle headlight power problem? |
The headlight on this bike is powered directly from the alternator. The power does not go through the regulator or rectifier that control the battery charging system and the other lights. I am looking for anyone who knows what ac voltage and current the alternator can be expected to output at a given rpm. I am measuring values up to abour 20 Vac at 5,000 rpm on the high beam circuit. The low beam circuit measures less because of the resistor in the circuit. The bike has a 6 V battery. According to the tests in the Clymer manual, the rectifier and the regulator are in good working order. Does anybody have any knowledge of this electrical system? Thanks! I believe it is wired wrong.Run a hot wire after the rectifier to the head light switch and then try it.The head light elements may be burned out.Check them with a continuity meter.I believe the head light is designed to run on 6v dc not ac.Have a blessed day. Source(s): DE-x-tech. you said before, you were showing ac voltage at the h/l circut, correct? and i did just dig out my oldest clymer on xr,s sorry only back to 78 and yes it does show running from stator,but notice it has a dedicated coil, damn book states,disconect batt and 2 pin connect at alt check pink and yellow wires at rx1 / 0.2-1.0 ohm, doesent say a thing about the yellow and white 3rd wire shown in schmatics,that being your h/l circut, but id imagine values should about the same,and you know a reading of infinity is not a good thing right? I have a 73, 74 and 75 XL 250. The voltage going to the headlight should be measured in DC. 20Volts sounds high for a 6Volt DC system. EDIT: I was outta gas this morning. Apparently, the hot weather in Vegas caused the tank to empty itself out. Now, I have gas in it. I have the values for you. You were right, it does measure in Vac, not Vdc. But, the voltage values are in the range I was expecting. At Idle of 1500 rpm, voltage across the headlight on High Beam is 4.5 Volts. At 7000 RPM the total voltage across the headlight on High Beam is 7.2 Volts. Edit 7:00PM PT: I just went thru the wiring diagram I found here -> http://oldmanhonda.com/mc/wiringdiagrams... It looks like the '75 diagram because it has hazard/blinkers on it. '73-'74 didnt have these equipped. Looking at the diagram, it reminded me of a few things. The regulator controls the voltage thru the ground (Green). If you follow the Green/White from the Regulator, it splits into all of the green grounds throughout the bike. You should not find a voltage higher than say 8Volts anywhere in the system when running. (Excluding Coil/Spark Plugs) It sounds like your voltage regulator is the first troubleshooting step. If I were trying to fix it on my bike, that is where I would start. Then Rectifier, then Alternator pieces. One last Edit 9:00PM PT: I talked with my dad tonight, he was a Honda mechanic in the 60's. He said, standard procedure was to change out the diode pack (Rectifier) first. Even if they thought it was the regulator, most times, it was the rectifier causing the problem. |
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