no brake light

I just bought an 85 yamaha xj700 maxim. The bike runs and rides great, but it has no brake lights, the tach and neutral lights quit working, (after trying to mess with the brake light), and the wiring under the seat is a mess. Any ideas or suggestions? O, and I'm new here from Indiana... hello

 

Sounds like 'lectricity- that is magic.
Others here will offer better advice but; start by checking your fuses, on my XJ650 they are under the seat. Then check your bulbs. Then look at the spaghetti that is your wiring, something may have lost its shielding and is grounding out, or a wire (or two) may be broken.
Welcome to the community, pay attention to what advice is given, and keep asking questions.

 

Thanks for the advice. The fuses and bulbs are all good.. I guess next is to play with a rats nest of wires..

 

There are fuses for the XJ700 located in the instrument cluster. Just wanted to be sure you found those also. If it's an airhead, the signal fuse applies power to the brake light, oil light, neutral light, tach, horn, and flasher. Water cooled the fuse does the same function, but is labeled flasher fuse. Both are 15 amp.

As for no brake light there are two switches, one for the front and rear brake and associated wiring. The switches are wired in parallel, so they would have to both be bad if neither activates the brake light with functioning wiring, which is possible on such an old bike. The rear brake switch is adjustable via a nut and a spring that pulls on a plunger to close the contacts in the switch, which would then route 12v to the brake light bulbs.

The more likely cause would be the single wire that feeds the brake light. I believe (not sure) but on both the air head and water cooled versions there is a tail light harness with bullet connectors that mate with the main harness and the tail light assembly.

Once you get the neutral light, oil light etc working again you can use a DMM to check for voltage to the brake light. On the air head the yellow wire should have 12V in respect to chassis ground when either the front or rear brake is depressed. On the water cooled the print I have shows the brake wire to be Green/Yellow. If you get 12V here, then time to check the harness and tail light assembly for good connections.

If no 12v then check out power to the switches and that the switches close as they should when the pedal or lever is depressed. The rear brake switch is more accessible, so it would be easer to start there.

 

Thanks. Looks like I got some wiring to mess with today. looks like the previous owner done away with the harness to the back end.. turn signals, brake light, etc. and wired it in himself. Sounds like a nightmare to me...

 

Thanks for all the help. Do to your knowledge, I now have a working tach, neutral light, and brake lights. Your input is much appreciated.

 

If you cant figure out your brake light a friend of mine just started retailing a safety device its a tail light bulb that has a motion sensor in it you let up on the gas or hit the brakes it comes on. They just started selling them in his retail store they are like 59 bucks very expensive but he has been selling quite a few of them.

 

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If you cant figure out your brake light a friend of mine just started retailing a safety device its a tail light bulb that has a motion sensor in it you let up on the gas or hit the brakes it comes on. They just started selling them in his retail store they are like 59 bucks very expensive but he has been selling quite a few of them.
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really--? , is that for real, or is it april 1st ...... surely that would have to have a permanent supply to it,
stu