No Spark Issue 1979 XS1100 *Newbie*

[asenovkz]

Hello everyone, I am new to this forum and hope I am posting in the correct spot.

I have a 1979 XS1100 that I have purchased a few months ago as a project bike. When I got the bike it was in rough shape (dirty and neglected) but it did have power and everything worked properly. When I rebuilt the carbs I got it to run and everything was OK. Then all of a sudden one of the main fuses kept blowing, upon replacing it would have spark again until a short time after where the fuses were ok but got no spark. I decided to buy a new fuse assembly and installed with no issues. Tried to fire her up but still no spark. Initially I thought it was the battery, so I installed a brand new one that was reading 13.2 V but still no spark. I tested the voltage to the fuses and the one on the far left was reading over 12V, but the remaining 3 were all around 11.85 V. I also tested to make sure the coils were getting power and they were. Im not great with electrical so any help would be very appreciated!

[red bandit]

Take apart and clean every electrical connection on the bike including the ignition switch and the kill switch. After that lets see what problems you have.

[DiverRay]

Don't forget about all the ground wires!! Most are on the reg/rec.
How did you check for spark? easy way is remove one plug, lay it on the head with plug wire connected, and turn the bike over. the other plugs should still be connected as well. If still no spark, check pickup coil wires under the left crank cover.
If the ignition fuse was the one shorting, you may now have a bad 2H7 ignition control module.
Last may be burned wires inside the loom. I did have a bike that did that, took out the headlights.

[asenovkz]

I will be checking all of the things mentioned. I will keep you guys posted!

[DiverRay]

Then check the kill switch on the handlebar. Known problem with old bikes. You can "bypass" it with a short jumper at the connector on the right side of the frame.

[asenovkz]

Then check the kill switch on the handlebar. Known problem with old bikes. You can "bypass" it with a short jumper at the connector on the right side of the frame.

It did have a starter button issue in the past. When I pressed the button nothing would happen. I re-soldered the connections, replaced the button, and also soldered the 2 wires together to make the kill switch permanently in the ON position. It did have spark after that was done, it also ran for a short time after. I only have time to work on the bike so much per day so these things were done incrementally. But it just seems like it sparks when it wants to, one day it may work and the next day nothing.

I did check the pickup coil wires (red wire in picture) and it did have voltage.

From previous forums I have read that if the voltage is under ~12.4 it would not produce spark either way. This is why I was confused when I measured the fuse voltage, why would one fuse show over 12V while the other 3 have 11.85V? Is it high resistance in the wires i.e corrosion ect?

[Radioguylogs]

It did have a starter button issue in the past. When I pressed the button nothing would happen. I re-soldered the connections, replaced the button, and also soldered the 2 wires together to make the kill switch permanently in the ON position. It did have spark after that was done, it also ran for a short time after. I only have time to work on the bike so much per day so these things were done incrementally. But it just seems like it sparks when it wants to, one day it may work and the next day nothing.

I did check the pickup coil wires (red wire in picture) and it did have voltage.

From previous forums I have read that if the voltage is under ~12.4 it would not produce spark either way. This is why I was confused when I measured the fuse voltage, why would one fuse show over 12V while the other 3 have 11.85V? Is it high resistance in the wires i.e corrosion ect?

(1) FYI, That's not a pick-up wire in the picture. The pick-ups are inside the LH engine cover, and the wires inside the cover are constantly flexing so they become a common cause for "No Spark ". Note there are two pick-up coils, most likely only one will fail at a time, so two cylinders have spark and two won't. You can easily measure the resistance of the pick-up coils at the IGN Module connector for a quick diagnosis, but it is more helpful to pull the LH cover off the engine and pull on each wire. You will easily see an hourglass shape in the insulation if the conductors inside have broken.*

(2) In an unrelated subject, I believe one fuse covers the power before it goes to the IGN switch. The other three 3 are returned from the IGN Switch, so they have more losses.

(3) BTW, You might consider disassembling and cleaning the Kill Switch rather than soldering the wires together as a permanent solution.

*Don't forget each IGN Coil fires two plugs, and both plugs have to be grounded for them to fire. If I have all the plugs are hanging outside the engine, I connect a battery jumper cable between the threads of 1-4 and another between 2-3.

[Bax]

asenovkz Attached pic shows two easy tests to rule out issues. The ballast resistor is an easy point to test. Hope this helps, if not post up your test results and we can go from there.......

---Bax

[TopCatGr58]

Just another note, the minimum voltage for the TCI (Transistor Controlled Ignition-module) is about 10.5 volts, so with yours just below 12.0, it should still work.

[asenovkz]

Thank you for the responses everyone! I have been very busy lately but I did manage to check out the pickup wires. I noticed they were TIGHTLY zip tied all over the place (probably 6-7 zip ties total) and it actually managed to eat through the wire insulation. One of the wires was indeed broken so I will be fixing it soon. I was thinking of just installing brand new wires since the current ones are super soft and and have a gummy feel to them.

[DiverRay]

The wire NEED to be "soft". They must flex a LOT, and it's hard to get the correct type of wire for them. If you follow the wires, you will see they are about 10" long, and then go to the "normal" wires in the harness. The normal wire has 9 or 11 wires in the bundle for a single wire. The wires at the pickup coils have about 21 to 30 wires, much finer than normal.
You can try to find test lead wire as a replacement, that is close to what Yamaha used. The insulation will be thicker, so it may be a problem. DO NOT crimp the new wires tightly on the plate!!! That is the reason they go bad! I had a brand new '78 that had one wire go out, and after the repair at the dealer I loosened up the crimps and never had another problem. I did try to get the problem to Yamaha through the shop, but never heard anything. That was "normal" for the time. Honda, Yamaha, etc. built the bikes, and the owners dealt with any problems.

[Bax]

I'm moving away from this rotating pickup assembly on my bike so I won't do a product test but this wire should be a suitable replacement for the OEM flex wire to the pickups.

Low-Voltage High-Temperature Wire, with Silicone Insulation, 26 Wire Gauge | McMaster-Carr

---Bax

[cajun31]

My two cents.... i suggest a flexible fix.
20 AWG 1 CONDUCTOR -600V FR JACKET - P/N 2001EM06 (coilcablespecialist.com)