1976 Yamaha LB 50 Chappy Lighting System

#1
Have a 1976 Yamaha LB 50 Chappy. Headlight works. Brake lights and turn signals only work when in neutral and engine revving at high level. Horn not working. Battery reading 7ish volts with engine off. Trying to figure out why brake lights and turn signals don't work unless engine is revving.
 

DaddyJohn

Well-Known Member
#2
Maybe this will help. I have a Yamaha DT250, and it's headlight and gauge lights are powered by the alternator, and the tail/signals/horn are powered by the battery. This leads to some some circuits only working with the engine running vs. some not. Also, some reacting to revving vs some not. You have a different machine, so those details may not match-up, but you might have similar circuit separation going on.

Here's a (unfortunately black and white) wiring diagram:

https://www.classiccycles.org/media//DIR_1653304/DIR_1792956/7b4ebf4db60cffe5ffff81d6ffffe417.pdf
 
#3
ok worked as a motorcycle mechanic sense 1973! lol spent several yrs at a Yamaha dealer . your tail light. and turn signals def run off of battery . so make sure you have 6volt?? bulbs installed not 12v. check for poor ground connections ? horns freeze up from sitting all the time .
 
#4
Maybe this will help. I have a Yamaha DT250, and it's headlight and gauge lights are powered by the alternator, and the tail/signals/horn are powered by the battery. This leads to some some circuits only working with the engine running vs. some not. Also, some reacting to revving vs some not. You have a different machine, so those details may not match-up, but you might have similar circuit separation going on.

Here's a (unfortunately black and white) wiring diagram:

https://www.classiccycles.org/media//DIR_1653304/DIR_1792956/7b4ebf4db60cffe5ffff81d6ffffe417.pdf
Thanks! That's what I was thinking. Maybe I have a weak cell in the battery because that is what I'm seeing.
 
#5
ok worked as a motorcycle mechanic sense 1973! lol spent several yrs at a Yamaha dealer . your tail light. and turn signals def run off of battery . so make sure you have 6volt?? bulbs installed not 12v. check for poor ground connections ? horns freeze up from sitting all the time .
Thank you. I've checked the battery and it actually reads over 6 volts. Does that make sense? I will check the bulbs but they have worked in the past. I've had multiple Chappy's in my life and the horns are always tempermental! I checked the rear ground point on the tail light assembly and had to really sand off some oxidation. Also checked where the battery grounds and it looked good. Are there any other locations I can check?
 
#6
make sure the ts themselves have good grounds . also the power for the ts goes through the flasher!! try a new one also unless trying to stay oem?? switch everything u can to led!! takes much less power! led ts require a led flasher>> oem flasher relies on resistance. through the bulbs to work led bulbs wont provide enough ohms resistance to flash properly.
 
#8
make sure the ts themselves have good grounds . also the power for the ts goes through the flasher!! try a new one also unless trying to stay oem?? switch everything u can to led!! takes much less power! led ts require a led flasher>> oem flasher relies on resistance. through the bulbs to work led bulbs wont provide enough ohms resistance to flash properly.
It's not possible to replace my current bulbs with LED? If so, what would the LEDs be to match?
 
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#13
yes u can get 6volt led bulbs
Would I still need to install an LED flasher? Is there a flasher on there now that isn't compatible with LEDs that I must change out? Sorry for so many questions. Its just really nice to have someone who really knows there stuff to bounce things off of before I go bumbling in there blind.
 

DaddyJohn

Well-Known Member
#15
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