82 XJ 650 - Modifying Wireharness for Engine Test Fire (without re-installing it in the Frame)

Hey Fam,

The mechanical/fuel systems are nearly a go - last step is to add back in the oil.

The wiring harness that I completely pulled off the bike looks to have been hacked on quite a bit (especially around the crank sensor plug and wires.)

My goal is to test fire the engine without putting it back into the frame, as after a full motor rebuild, who knows what problems I may encounter.

Has anyone marked up the wiring schematic with what connections and what jumpers are needed for using a temporary switched connection from the battery to the starter, and the necessary ignition system?

There will need to be a common ground block of some sort.

I expect the voltage regulator, coils, starter to be connected to battery switched-contactor of some sort, but are there sensors/fuses/instrument cluster pieces that MUST be connected or can those all be jumpered out?

I can take a stab at marking up the schematic on my own and post some photos of the wiring harness as I prep it, but if someone has done a similar exercise it would save me HOURS (likely Days) of work, and the potential risk of fire or melting likely important components lol

 

I saw some posts on using newer aftermarket/smart wiring harnesses on the XJ a few years ago when I first got this project bike. It might be time to just bit the bullet and make the switch, the documentation would be a lot clearer on how to accomplish the goal as stated above, however, I would prefer to delay that decision until I know the mechanical side of things has been tested and is ready for reinstalling into the frame. That said, I'm open to reviewing posts in that vein for info if anyone has seen one that would be helpful to the questions above

 

This is the schematic I found

 

The fuse box is in a poor state - but is the ignition fuse needed for a test fire, or is it to protect the switches on the handlebars that I'm not planning on wiring in?



Along with the clutch sensor there is this connector that has been bridged out, not sure what this was originally to? (The clutch sensor itself will need a new connector at some point...)



This looks like the biggest issue, not sure it will be usable, but at least I know what connections need to be made here:



These three wires look modified, does the clutch sensor have 3 wires going to it, out of the ignitor wiring harness? Or is this to something else?



Any idea what these three cut wires in the middle originally went to?



What about this red wire, where does this go to?

 

Just for context, I've put this in some other threads, but I bought this bike 2 years ago. It was not running, the carbs were off (water in cylinder #1, so did a full motor rebuild). I was told that it was running before the carb issue, so (a loose assumption) that the wiring harness should be mostly in working order. I disassembled the bike down to the frame and then had some health issues that pushed back me being able to do any work on it, but now am back in the saddle and making good forward progress. The motor and carbs are all rebuilt, and I want to test fire the engine to confirm it is working well before moving on to electrical/frame/tank/wheels/seat.

 

You've obviously worked hard to get the engine rebuilt, I would get the frame done now and put the engine in it. Then get a workshop manual and check out the loom - how are you going to do it otherwise? Without a decent exhaust you won't hear any untoward noises from the engine, you won't test the gears or the clutch.
Welcome, btw

 

I think I'm not so worried about gears and clutch - I'm worried about oil leaks, all 4 cylinders firing, confirming ignition/starter/timing; that said, you make a good point about the exhaust noise - but I could have sworn I've seen engine mounting frames for testing engines, but you may be correct the bikes frame is already custom made for that - just a difficult thing to do on my own and after many surgeries I'm not as strong as I used to be.

Specifically - what did you mean by a 'workshop manual'? Do you just mean the Haynes manual? my quick review of it was that it was great for the troubleshooting the componentry, but the loom itself looks like more of a trial and error endeavor, much less figuring out which components can be jumped out to allow for an engine start.

 

Mount the engine on its side and lower the frame over it.
Workshop manual would be a Haynes or similar - no way you will fault find all the switches and relays without it. The handlebar switches are invariably failing, as will the individual cables to them - that is if they haven't been butchered...
If you want to make all the connectors back to original click on xjforever at the top rh corner of this page.

 

The thing I haven't quite sorted yet are the plan for grounding/earthing - open to suggestions.

After your suggestion I went back to the Haynes manual, and have been doing some studying. The main unlock for me was figuring out that I have an XJ650-J. There are subtle wiring/wire color differences from the UK schematic I was looking at and everything makes much more sense now.

I've chased down about half of the questions in the photos I had above. The bridged out connector was the side-stand switch.

The manual has good diagnostic indicators for testing if any of the below items are not working as expected.

My first pass review indicates I need the:

• Starter Circuit (Relay, Cutoff Relay, and switch)
  
  • probably need an inline fuse
• Bridge the key switch and kill switch
  
• Alternator/Rectifier/Battery circuit, normal connections and grounds
  
  • probably need an inline fuse
• TCI/Ignitor/Plugs/Timing Pickups

It looks like the rest of the loom/components really aren't needed (until later). I have a good 12v diagnostic probe, and have already started taping and labeling the components mentioned above, and the wire colors (so far) are all matching the appropriate components, and so far conductivity tests haven't shown any issues within the loom itself.

It appears the most difficult part (for me) will be getting the engine in the frame and connecting up the exhaust header.

I'll keep plugging away and come back if I hit any snags I can't sort out. Thanks for the encouragement/help so far