A different headlight question

madmaxer

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so, I haven’t been around in a long time, life gets complicated as everyone knows so I won’t go into that. Haha
I have been chipping away at my cafe for the last several years, I’ll call it an 81SH, runs like a top. Without listing it all, I believe I have rebuilt or replaced almost every component on the bike, literally. As sweet as it is, the ignition has been cutting out randomly, after I roll to a stop and shake my head, cycle the key, because I can, it will restart. It may now go 100yds or 20 miles and do it again. Get it back to the shop shut it down, start it up and it purrs.
Have had a some weak connections, that I chased and soldered up, but is still acts as if it’s losing ground. Suspecting an intermittent broken wire, I just replaced the harness with a new one from mike’s, and my first impression was wow! Such nice tight connections! Way better than the “clean” ones I had. Haven’t rode it yet but I think it will be an improvement and maybe a cure.
Here’s my problem, the headlight comes on with the key, no matter what, SR and LR test good, but the light will key on even if I unplug the safety relay. Only when I unplug the RLD will it go out. I just don’t understand how the dimmer is getting power with the relay unplugged. Btw it is currently electric start only, so I like the light off until it starts.
I know I could install a switch, but I liked the way it is supposed to work.

Any input would be greatly appreciated.
 
My buddy's '80 SPII has the same issue with a MikesXS replacement harness. There's obviously a glitch in them somewhere. We haven't attempted to track it down yet because it looks like it may involve unwrapping major portions of the harness to find that incorrect connection.
 
Your intermittent ignition could be the TCI box. It’s 40 years old. If the problem still exists, it would be my suspect #1.

I thought so also, but I have two, maybe three? Swapping them out made no difference,,so I kinda wrote that off,,,they could all be bad I suppose, but even if they were would they all fail with the same symptoms?
Thanks for the suggestion,,,,
 
They are all vintage tho,,,lol

..and I agree, if the harness doesn’t work I would shoot for a newer one, again.
 
I thought so also, but I have two, maybe three? Swapping them out made no difference,,so I kinda wrote that off,,,they could all be bad I suppose, but even if they were would they all fail with the same symptoms?
Thanks for the suggestion,,,,
No, I would not expect them all to behave the same way.
 
Possible culprits.
Weak magnet on rotor
intermittent short in retarded pickup.
intermittent keyswitch.
intermittent fuse
bad cell in battery or dirty connection.
gimpy coil
gimpy kill switch

a 12v led attached to a length of wire with alligator clips is you friend. put the led where you can see it while riding to test for power at different components. Keyswitch ,fuse block ,coils etc.

Something non electrical.
 
Alternator new, however new rotor did cause a near catastrophic failure, as the commutator plate was screwed on as opposed to riveted as oem . Screw came out and trashed the plate broke a brush and brush holder. Replace them all with good used. Charging system is currently working well.

Don’t know how I would discover an intermittent short in the pickup,,

Disassembled cleaned and reassembled ignition switch, test well.

New fuse box looks and feels, tight and right, test well.

Battery was holding and performing well till this winter now it’s not holding a charge, new one on the way.

Coils new, with spares on hand, swapping has no effect.

Kill switch clean and static tests good,,,

Motor has about 1500 mos on it since Re build, 650 cc jugs, pistons, bearings, shell 1 cam, new springs, valves seated, porting cleaned up. Exhaust system, and currently a nice set of bs 38’s (what a difference a needle jet O-ring makes!) runs awesome when it does.

I like your suggestion below! I gotta do that if this keeps happening

Thanks!

a 12v led attached to a length of wire with alligator clips is you friend. put the led where you can see it while riding to test for power at different components. Keyswitch ,fuse block ,coils etc.
 
I hate intermittent problems.

TCI box needs a minimum voltage. I don't think it's the battery but fingers crossed could be.

Is it a new rotor or a rewind ? Magnet could be gympy. Been reports of that here.

Sounds like you have most of the bases covered.

I think the test for the magnet is to run with the rotor unpowered to eliminate the rotor magnetic field that the pickup magnet has to overcome.

Keep us posted.
 
Today I read the tech thread on TCI rebuilding/ repairing, this was one I missed , good news was both of the TCI units that were on the bench looked good, and tested well.
No signs of heat, all diodes equal and proper
Soldering looks good, a little sealer flaking off, but I was surprised how fresh it all looked.

Just glad I don’t have to replace the diodes.
 
I would attempt to trace where the power to the headlight is coming from. When tracing power or continuity on a harness I attach a sewing needle or pin to the multimeter probe so I can spear the wires through the insulation so I don't have to cut and re-solder. Is the wrapping on the harness easy to remove then re-tape? Some are easier than others.
 
My buddy's '80 SPII has the same issue with a MikesXS replacement harness. There's obviously a glitch in them somewhere. We haven't attempted to track it down yet because it looks like it may involve unwrapping major portions of the harness to find that incorrect connection.
 
Well 5twins you are correct. I discovered two miss wired circuits in the new harness. I should say identified, because I am unwilling to unwrap and chase them down.

First the headhead light circuit is powered by the main circuit, (red) and is hot with the key on as well as all ( blue black) wires. This is true with all fuses removed except the main. As a result the headlight relay and RLD are overridden.
Second the blue wire powering the gauge lights is dead, suggesting it’s not connected to the blueblack lighting circuit.

My solution,,, I installed a toggle to the low beam, so I can have it off for startup, highbeam works when asked for at all times independent of the toggle.
Jumped the blue switched lighting circuit from the key switch to the gauges and they now work as they should.

So I am a little disappointed it didn’t work like a dream, however for the price, the fresh, tight, new connections and wire, imo are well worth the price of admission.

One note while most of the wire colors in the new harness are correct to original, several are not, so to trace and verify I had to revert to the original to be sure,,,,

So currently everything seems to work as it should, weather or not it cured my cutting out problem has yet to be seen. Warm weather coming,,,,,,,
 
Ok full disclosure, got er out today, idling and reving great, troll out of the shop, pause, admire the sound, and the steady idle, all shined up, give it a little Rev and wham! it shits on me ! Lol after all that tightening of the electronics. Ok I say, wtf! Swap out the TCI and boom it’s back, I know I swapped these TCIs in and out before and it made no difference, but today it did.
Took it out and it ran better than it ever has! Omg! Smooth from the bottom up! Pulls awesome and drops to a sweet idle. Everything just works better. Happy camper right here! Thanks for the advice and help everyone!
 
5002D1F6-DC43-408E-869F-86BD140CEAE0.jpeg
 
A note the stator wiring harness which also has the pickup wires may have issues near the sprocket area, several of us have cured intermittent ignition by finding and repairing wires "hanging by a thread" there.
 
so, I haven’t been around in a long time, life gets complicated as everyone knows so I won’t go into that. Haha
I have been chipping away at my cafe for the last several years, I’ll call it an 81SH, runs like a top. Without listing it all, I believe I have rebuilt or replaced almost every component on the bike, literally. As sweet as it is, the ignition has been cutting out randomly, after I roll to a stop and shake my head, cycle the key, because I can, it will restart. It may now go 100yds or 20 miles and do it again. Get it back to the shop shut it down, start it up and it purrs.
Have had a some weak connections, that I chased and soldered up, but is still acts as if it’s losing ground. Suspecting an intermittent broken wire, I just replaced the harness with a new one from mike’s, and my first impression was wow! Such nice tight connections! Way better than the “clean” ones I had. Haven’t rode it yet but I think it will be an improvement and maybe a cure.
Here’s my problem, the headlight comes on with the key, no matter what, SR and LR test good, but the light will key on even if I unplug the safety relay. Only when I unplug the RLD will it go out. I just don’t understand how the dimmer is getting power with the relay unplugged. Btw it is currently electric start only, so I like the light off until it starts.
I know I could install a switch, but I liked the way it is supposed to work.

Any input would be greatly appreciated.

Another possible cause for random ignition failure/recovery is low water in one or more battery cells - ask me how I know. If you have a TCI ignition system instead of points, it pretty much needs full battery voltage to operate reliably.
 
Just out of curiosity what do you have your idle set at? These bikes idle high, idle set to low will cause them to die at a stop occasionally. They should idle at about 1200(+-50) anything below that can cause the bike to die at a stop. I say this because most peoples inclination is to set the idle much lower and then seek electromechanical solutions to the constant dying. Mine idles happily a little closer to 1275 without dying, I used to set it much lower and the same problem.
 
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