1981 xj750 seca No start/No spark

I have a 1981 xj750 seca, got it for free owner said it ran when he parked it. I have cleaned the carburetor, spotless and correctly. The wiring though is a mess.... I removed the headlight & Atari speedo as well as the big connector between the harness and Speedo, if I read the wiring diagram correctly i Should not need that big connector plugged into anything, I removed as much stuff as possible cosmetics wise, as I would like to make a cafe racer. The bike has been sitting for 20 years or so. There's are multiple wires snipped, missing, and simply unplugged. The start button will not crank it over as do I not hear a click either from the starter solenoid, but I CAN get it to crank over if I bypass by applying power to the starter solenoid, I am getting no spark either way, It has been sitting a very very long time, alot of wires have been cut or 3 way soldered together (whhhyyyyyy!?!?!? Lol) anyhow, kind of at a stand still and I really like this bike and would love to finish, but... Stuck in a sand trap haha

 

there is a wiring bypass diagram for removing the atari that has to be done for bike to run.
only other choice is minimal wiring

Here's the wiring mods to remove the rectangular instruments

 

minimal wiring download the pdf file white page

 

what you need to do is check your fuses you shouldreplace with new blade fuse holder
Your Fuse Box -- A Ticking Bomb??? By: Rick Massey

also ohm out your ignition system which includes ignition coils spark plug caps and pickup coils
check your relays to see if present and working side stand switch may be the issue .
specs are found in this thread
The Ultimate Relay, Switch, Sensor, and Diodes Guide

if you have voltage at ignition fuse check connector at tci red/white wire for 12 volts if not there check the connector
from right control it is in head light bucket you want to check for 12 volts on the red/white wire up and back this voltage it controled from the run/kill switch back probe the connector.
I would advise removing control and cleaning the starter button and run/kill switch with electronic spray and lube with silicon spray (not the dry spray) or dielectric grease.

to test starter button remove 2 position connector from solenoid hook meter to blue wire and positive of battery press starter button you should get 12 volts.
check connector (mentioned above) to see if the starter button runs to ground by wire or handle bars . there will be a black wire running from control to connector and should be a black wire in the mating harness connector running to ground.
if starter button is good reconnect the solinoid connector and back probe it to see if you have 12 volts at the connector both positions blue wire will be lower than red/white wire if no voltage on blue wire solenoid is bad . if no voltage on red/white wire check to see if the starter cutoff relay is working or present.

your ignition system works off of the red/white wire it goes from fuse to run switch then down to coils and tci and to a relay then to solenoid to starter button .

also your battery needs to be fully charged do a voltage drop test on it hook meter to battery check voltage then press starter button if voltage dropss below 9.8 to 10 volts you will not get a spark.

 

If I decided not to do the Atari wiring bypass, and I DO decide to do the minimal wirong, what do I do with the rest of the wires? I'm going to do the minimal wiring, so what do I do with the others I wont be using?

 

Price was right.....

BUT----how come people never say "It stopped when I parked it"? Isn't that more accurate?

 

Do I need to do both of those things? Or just 1?

 

If you go with the minimal wiring, you can just leave the others in for now, just disconnect all unused ends.

Some people undo all the wrapping, pull the extra wires out completely and re-wrap with new tape.

Make sure that you have current through the ignition switch... It almost sounds like you are completing just the starter motor circuit but not the ignition/run circuit

 

which ever one you understand will work they are the same thing just remember to use the existing pickup coil harness to tci and use the other connector in the tci as a guide for new wires or use it too

 

So by looking at the minimal wiring diagram I see it goes to the headlight & tailight. So I need a headlight installed for it to run? And I can literally remove every extra wire thats not listed in the minimal wiring diagram?

 

no all you need for it to run is the starter circuit and ignition also connect the voltage regulator/charging system

if you look at the green diagram you need starter switch to solenoid and ground then starter heavy wires, solid red wires , red/white wires, and brown wire from key to ignition fuse to kill switch and the brown wire back to the voltage regulator along with charging system wiring ( stator and brushes) and you can drive down the road.

yes every wire not used can be removed you may want to retain lighting and directional wires . the purpose of the min wiring is to remove relays and safety switches , side stand safety switch sidestand relay, starter safety relay headlight relay (if you have one). so if you are retaining wiring wiwith relays you will have to jumper across conectors where relay goes.

 

also the tci connections of course that would be to pickup coils 3 wire harness and from tci to ignition coils

 

do you have an original wiring diagram?