1985 Xj700 only has power to blinkers and taillight

Hey guys

I recently purchased a 1985 Yamaha XJ700 project bike. I bought the bike not running. The guy I bought the bike from said that he bought it running and that he went out to start it one day and it "just wouldn't do anything".

When I got the bike home the first thing I did was check fluid levels and try to start it. I noticed that the starter button was wired together and that the engine would turn over (without a spark) as soon as the ignition switch was switched to on and that there was no power to headlight, instrument cluster, taillight and front/rear blinkers. To avoid causing further problems I didn't try again and started repairs.

I removed the instrument cluster/indicator panel cover to check the fuses and the 15amp "head" fuse was bypassed with speaker wire and the wall of the housing around the fuse clip was melted through. Looked old and had been that way for a minute. The other two fuses which are supposed to be 10amp and 15amp had a 25amp and a 75amp fuse in their place. I replaced the fuses with the ones required and installed an inline fuse holder for the damaged 15amp since I couldn't repair the housing.

I have installed a new starter solenoid, ignition switch, left and right hand controls, clutch safety sensor, battery and repaired all damaged/exposed wiring. I have not replaced any relays, ignitors etc.. the wiring harness, coils and attachments are all factory.

As far as mechanical repairs go, I stripped the bike to the frame, leaving the engine, and rebuilt the carbs plus replaced all engine gaskets/plugs and inspected the engine in the process and it looks great with 29k miles. Stripped it, painted it, and reassembled everything except the fuel tank.

Now with everything back together (besides the fuel tank), I only have power to blinkers and taillight. Blinkers won't flash, just constant, and the taillight is in the same state. No indicator lights, no headlight, no control functions etc..

I am not sure where to look next. I have noticed that there is a 4 wire cable unplugged near the battery box but I cant find its mating end. It has a red/yellow, black/yellow, blue/yellow, and black wire. The original airbox was removed and replaced with pod filters at some point and it could have had something to do with the airbox but I highly doubt it.

This is my second project bike so I'm no expert. Thanks in advance for any help!

 

So you bought a project bike - now you should buy a manual. Then a dvm (digital volt meter), and learn how to use it to follow a wiring diagram. I don't have a manual for your bike so would be guessing in any reply to you, I would suggest your rectifier/voltage regulator is missing though. However, this wouldn't create the issue you're seeing.
If you want a world of frustration wait for the guesswork to start - if you want to get your project running do the above - best advice I can give.
Let us all know how you're getting on.

 

I started with the basics and checked all fuses and relays. They turned out to be performing properly. Wiggled a few wires and cleaned a few connections in the headlight housing and like magic, it’s alive and functioning in all areas. Tried to pinpoint what connection was faulty but I can’t recreate it. May have been a bad contact on a fuse. Anyway, problem solved without breaking a sweat. Thanks for taking the time to reply.

 

not sure about the 700's , but blue/yellow-- black yellow are usually clutch interlock switch.
which then run to the diode block, maybe the diode block is missing

 

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I’m not sure if you can identify what it might be from these photos, but I’ve attached them anyway. Plan to review the wiring diagram later today.

 

Are you sure those are yellows and not whites? Looking at the wiring diagram, that might be the sidestand relay. The sidestand relay (44 on the wiring diagram) looks like it's R/W, B/W, L/Y, and B.

When I go out to the garage I'll have a look around my 700 and see if I can find out more.

 

They could be white - the color is pretty distorted from age. Side stand relay would make sense. The previous owner did a lot of botched electrical work to bypass a lot in an attempt to find the problem. If it is the side stand relay, can it be left off without issues?

Turns out the starter motor is bad. Starter solenoid would just click with every attempt to start- checked voltage and all looked well but no response from the starter motor. A couple light taps on the starter motor while pressing the starter button and the engine turned over and started. Going to rebuild and reinstall.