'78 R100s kill switch fried

[oskkar]

That was my initial thought. But no, the poles are located same as the Panasonic LC-X1228P it replaced.

[Kurt in S.A.]

What other maintenance have you done? The position of the coils under the tank puts the powered terminals very close to the tunnel of the tank. DAMHIK.

Kurt

[oskkar]

Hmm. I did remove the tank to top off the brake fluid about a week ago while I was waiting for the new battery. ..

[Rob Frankham]

Oskkar -

There's something very strange going on there. It shouldn't be possible for (any) current to get to the kill switch without the ignition switch on. Can't think of anything that would cause this issue unless there are two distinct faults, one short circuit and the other involving the ignition switch. I Really think that you n(or someone) needs to go through the electrics to find out what exactly is going on.

gspd -

If the battery were to be connected in reverse, there would be an immediate and destructive short circuit but this would be through the diode board, which would be destroyed. I can see no reason why there should be any current flow through the kill switch, especially if the ignition switch is off.

Rob

[barryh]

Without the ignition switch being on and assuming the ignition switch is not faulty and is wired correctly, the only way I can see a live feed getting to the ignition circuit is via a fault in one of the other items that link in to that circuit i.e the buzzer relay and the starter relay. Only one of those items has an unswitched feed from the battery and that's the starter relay. So that's what I would check first. Still can't see how the starter relay would cause that but this is one weird fault and it will only surrender to a strict logical approach.

[oskkar]

Finally had time to give the bike electrics a full inspection.

As preliminary matter, am beginning to wonder if I did turn on the ignition switch initially. This given what Rob and barryh noted seems more likely to me now. Am proceeding now as if I did.

Some observations;

1. Overall electrics are much closer to stock than I thought.
2. Most of the visual evidence of burnt wire is on the wire from ignition coil to kill switch. Have shown all locations in red on the wire diagram below.
3. Starter relay appears fine.
4. Coils tested:
Left Coil
Primary : 1.7 Ω
Secondary : 12.56 kΩ
Right Coil (Coil with burnt wire that runs to kill switch)
Primary : 1.6 Ω
Secondary : 13.57 kΩ

^Wiring Diagram 78 r60-r100s_v3c.jpg (286.12 KiB) Viewed 59709 times

Next steps;
I am going to replace the complete run of wires highlighted in green and blue/green on the wiring diagram. As a substitution for the damaged switch, I was going to either;

1. Install a 20amp on/off toggle at the location shown in diagram, or
2. Bypass/remove it completely and just connect the wire from the ignition coil directly to the starter wire.

Any thoughts on if its crazy talk to remove the run switch completely, or on what to replace it with would be greatly appreciated. I did try and fix the switch but too far gone and buying complete new right handlebar combination switch seemed little pricey.

Thanks,

[barryh]

Not crazy talk. I haven't used my kill switch once in 18 years, at least not deliberately, I just turn off with the ignition key.

[Rob Frankham]

A 'kill switch' is useful and is a requirement in some jurisdictions... necessary? no comment.

Rob

[oskkar]

I replaced all burnt wires, cleaned all connections, and installed simple on/off toggle in place of kill switch. I also made sure all wiring under tank was properly insulated. Bike is running very well now. THANKS to all for your help!

I did however have another issue with the right side swing arm bolt I was hoping to get the groups' thoughts on. Basically, it fell out while I was riding.

swing arm bolt on ground copy.jpg (418.6 KiB) Viewed 52661 times

I was going about 25 mph and felt the back end slide. I pulled into first gas station about 1/4 mile up, saw bolt was missing and then walked back and found the bolt on the ground couple hundred feet from where I first felt the slide. Genius I am I didn't have my tools with me and hand tightened the bolt and rode back home. Was lucky I was only couple miles away. Rode very slowly and stopped periodically to re-hand tighten. Was also very, very lucky I was at low speed when it came out. I have photo from when I was working on the electrics that shows the dust cover still on. So I'm assuming the bolt worked its way out over the course of 40 miles of riding at 30-50mph after the repair to the kill switch.

My question is do I need to remove rear wheel or anything else before I re-install the bolt, and is it unheard of for this to happen? I would note that I have never added grease in the cavity and it was pretty empty. Other than that I don't know what the cause could be.

I found the proper procedure in my Clymer's to space the swing arm evenly in frame and torque specs for the bolt and lock nut. Concern is that the frame in hole and in bearing don't seem perfectly aligned and don't want to force the bolt in and strip the threads if something is torqued.

Any thoughts appreciated.
Thanks much.

[Rob Frankham]

Not something I've seen happen before but I suppose that, if the locknut were to be left untorqued, it is quite likely that the pivot bolt would work it's way out.

You don't need to remove the wheel or swing arm to replace the pivot bolt but it would probably be a good idea to examine the bearings. If the bike has been ridden for a long time with the pivot loose, it isn't going to have done the races any good. It would also be advisable to check the threads. To examine these bearings you'll have to remove wheel and swing arm.

The adjustment of the bearings requires a fairly light torque on the pivot bolt itself so, for the adjustment to be accurate, the bolt needs to be free to turn in it's thread. Overtightened or undertightened bearings will not have a long life. It's a good idea to run a tap through the frame housing and run the bolt itself through a die to ensure that there is no resistance in the thread... especially if there is a chance the thread itself might have been damaged. I think the thread is a 14mm x 1mm but I'll have to check.

When the frame was built, it would have been welded together then the swing arm locagting points would have been accurately drilled using a jig so it's possible that the hole might not be exactly central in the frame bracket. Unless there are signs of damage to the frame itself, I wouldn't worry about it being slightly off centre.

My advice would be to strip the rear wheel and swing arm out of the frame, examine the bearings, threads and the pivots on both sides. Check that the pivots screw easily and freely right through the frame threads (and do anything else that needs doing in that area) then reassemble lubricating the bearings with lithium grease and making sure that the locknuts are tightened properly.

In passing, these bearings can be lubricated in situ by forcing grease down the central hole in the pivot bolt...

Rob

Edit... As I'm sure someone would have commented before long, I got the thread size wildly wrong above. It should be 20mm x 1.5mm. Teach me to check before I type!

R