1983 xj750K Maxim - No signal or brake light, No Horn/start...

A bit of background: Restoring this bike, which was stripped down but did have the original wire harness. Added a new fuse box. Used an engine and other parts like the LH & RH controls from a 1982 xj750J Maxim and gauges, headlight and signals from a 1982 xj650J Maxim. Installed a new battery that previously worked well in the 750 Maxim before switching parts over. Just finished installing all the components and wonder if there is some simple explanation why only a couple electrical components are working.

The only things that work are the gauge lights, Headlight, both low and high beam, and the tail light. Again no brake lights. The high bean (blue) indicator lights up properly, but the neutral does not...nor does both the signal and oil pressure indicator lights.

 

That's a lot of mix and match so there could be several possibilities. Since everything missing is related to "signal" power, a good place to start would be to check that voltage at the signal fuse to be sure you have 12V on both sides of it (key set to ON). If that is OK then pick one of the related circuits (the horn would be good) and verify you have 12V at the Br wire with the key set to ON.

 

Except for the horn, It’s all fixed! Appreciate the advice!

The horn did make a feeble sound on the 1st try, then nothing after trying the button again and again. Perhaps faulty button...or is there a relay I can replace?

 

So was it the signal fuse, connection, or something else?

There shouldn't be a separate relay unless a previous PO made a modification to upgrade the horns.

The horn button is likely, since there are two horns wired in parallel and you went from the feeble sound to nothing at all. The Br wire at the horn should have 12V supplied by the signal fuse, the P (pink) wire is pulled to ground by the horn switch. You could try grounding the pink wire at the horn to determine if the switch or wiring downstream is defective.

 

When switching out the old 8-pin terminal plug with the new one that fits the fuse wiring, I had crossed some wires, so signal was going to ignition instead of across the fuse to signal. Doh!


High Tone horn seems defective, no current (ohms) between the two prongs, whereas the low-tone has open current.

 

No continuity between the terminals indicates corroded contacts or a stuck diaphragm. There are quite a few threads on this site about trying to repair them, but the consensus seemed to be to upgrade.

Here is a nice YouTube link on how they work:

 

No spark. Not at any plug. Actually, the only spark I get is when I turn the ignition to on. There is no spark when trying to crank it over. I switched out the rectifier with a spare and back. Switched out the CDI with a spare and back. But with this CDI spare the only difference was that initial spark, when turning ignition to on, occurred in the right coil (Both wires 2 & 3) instead of the left coil (both wires 1 & 4). I’m getting continuity from coil connector to CDI connector on both coils.

Bad coil??? Bad ignition switch???

 

I would not suspect either. When the key is turned on one channel of the TCI is pulled low charging that coil. To keep from damaging the coil the TCI will switch to standby mode a couple of seconds after not receiving an input from the pick-up coils. When switching to standby that channel going high collapses the charged coil primary field and one spark results.

So, if the spark is occurring a second or two after the key is turned on I would suggest:

Check the battery voltage while cranking, it should stay above 10 volts. Anything less and the voltage to the coils is reduced sufficiently weakening the spark and making it difficult to see.
The ignition cutoff safety circuit could be defective. To isolate the ignition cutoff for troubleshooting purposes disconnect the B/W wire that goes to the TCI 6 pin connector. There should be a bullet connector near that wire making it easy to accomplish.
Ohm out the pick-up coils at the 6 pin connector that mates with the TCI. Gr to B and O to B should be 650 ohms +/- 20%

 

Thanks so much, again! Well, not only does it now have spark...it runs great! The problem was I had the wrong relay plugged in, the one below the rectifier.



Now, some final touches, like installing Xj750jM brake lines and refilling/bleeding the brake fluid and soon it’s going to be titled right after having the State Patrol inspect it.

 

Nice looking bike!

 

I LOVE! The redline on the speedo at 55 mph! Lol!

 

Just installed a used replacement High Tone horn and all I heard was that same feeble sound of the horn for about a second and then nothing. Tested from prong to prong and there was no ohm, but I tested it after the installation and should have done so prior to installing. Anyway, I'd like to keep the bike stock but it's temping to buy replacement horns that are louder.

 

I really like the horns on the 750 Seca that I have. They seem quite loud and are the only bike I have had that didn't have that scooter beep sound to it.

There are some posts on the forum where members seemed to restore the horn by adjusting the tone adjustment screw.

Some are taking them apart and cleaning them

And, I would try them connected directly to the battery (after checking continuity) just to rule out any issues with the bike wiring / switches.