1977 XS400 wiring loom question - solved

[TazioliBuilt]

not sure what I lost in the mess of the rebuild, have looked everywhere but I wonder if I ever had the wires to begin with.

Where does the rectifier wire up to?
Also, the last two wires in the last photo—I assume they go to the points ?

Thank you. My fuse wiring was destroyed when I got this auction bike. Not sure if part of the loom went with it.

 

[TazioliBuilt]

Please excuse my stupidity!!

Do I ground the brake switch to cancel or do I put power to it and ground it?

 

[BBS360]

First picture is the regulator. Easy answer is that it plugs into the harness. You haven't really said whether you have a wiring harness or not.
The regulator controls the alternator field coil and also has a positive supply and a ground wire.

The points plug into the orange and grey wires. Other ends should attach to the ignition coils.

The brake switches don't go to ground. The brake lights are grounded.

Grab the Yamaha and Haynes manuals from the threads at the top of the Garage. It'll help a lot.

 

[TazioliBuilt]

I thought I had lost a connector, it was in the sleeve.

I have three wiring harnesses. One has been built for racing, no lights, no brakes, no signals. I may use indicator lights for neutral and oil but I’m not concerned with that at the moment. Just got another 1977 XS400 tonight and will be swapping the engine over this week.

 

[xschris]

That bike is a 78 2-E Looks like it has already seen the usual cut up these bike tend to have. Hope the mufflers are still good. That would be a good score.

 

[Petew]

That bike is a 78 2-E Looks like it has already seen the usual cut up these bike tend to have. Hope the mufflers are still good. That would be a good score.

My 77D still has the original exhaust. I just wish I had the tank...

 

[TazioliBuilt]

That bike is a 78 2-E Looks like it has already seen the usual cut up these bike tend to have. Hope the mufflers are still good. That would be a good score.

Has 7/77 as build date

 

[Petew]

I love the wire wheels on the 782e. It looks like someone did rear sets on it too.

 

[TazioliBuilt]

Silly question because I’ll know tomorrow but can I run this engine to a Xs400d loom? I built the loom and this bike came with 3 molested looms that won’t work, thus the sale. I noticed the capacitors are different and that may be the only noticiable difference for me at the moment. My D has a single capacitor, this bike has a dual?

 

[TazioliBuilt]

That bike is a 78 2-E Looks like it has already seen the usual cut up these bike tend to have. Hope the mufflers are still good. That would be a good score.

Mufflers are top notch and I have another set that isn’t bad either.

 

[xschris]

77-78 motors are the same other than the 78 2-E was a kick start only bike. These both should have a double wire condenser. 77 bikes where built in 76 and 78 bikes where built in 77. The vin will also tell you what bike you have.

 

[TazioliBuilt]

77-78 motors are the same other than the 78 2-E was a kick start only bike. These both should have a double wire condenser. 77 bikes where built in 76 and 78 bikes where built in 77. The vin will also tell you what bike you have.

Do I need the neutral and oil switch wired in for the bike to run?

 

[BBS360]

They are not required, no.

As xchris said, they should all have "dual" condensers. Two wires, two combined capacitors in one unit.
A photo would help though, in case you are referring to something else.

 

[xschris]

Do I need the neutral and oil switch wired in for the bike to run?

They are a good thing to have working and I would not ride without them.

 

[TazioliBuilt]

It’s a race only bike for vintage flat track.
I don’t have spark but I have power to my ignition and start switch so I’m going to wire in a new fuse box and go from there. Little disappointed at the moment and the points look fine.

 

[TazioliBuilt]

Still no spark, going to add grounds and clean existing and go from there. New fuse assembly installed. It sparks when I turn the key on the left plug.

 

[TazioliBuilt]

Ok good spark left side only after fixing grounds. I played the swap game with the wires, no change. Going to swap right coil and go from there.

 

[TazioliBuilt]

Cut a hair off the plug wire of the replacement coil, swapped the connector over—attached to frame, wired it up and I have healthy spark on each side. Very pumped, it’s late so I’ll add fuel to the mix tomorrow and see how she turns over. First I’ll add more oil to the cylinders because I did it before all this spark fiasco stuff and I want a little more lube in there before I start kicking.

So I got this bike and engine two days ago I think and it had no loom attached. I put a loom I built to the frame and engine with factory key and stop switch. Proper grounding and a bad right side coil were my problems. I made sure my points could move properly and I gave them a wipe with 320 grit fairly quickly. All in all, pretty simple fix and fairly simple bike to wire up—very excited to race it and I still have another engine and bike I’m rebuilding proper For racing.