. I am only getting spark on two plugs. Both coils check out to be good.

I just purchased a 1980xj650. I am only getting spark on two plugs. Both coils check out to be good. The pig tail that is not giving off any spark is the one with the orange wire. I did notice after turning the motor a few times the coil that is hooked to the bad pig tail gets warm. Any ideas on what I should start looking at?

 

Check all of the connections like from the pickups on the gearchange side of the bike to the TCI and from the TCI to the coil pigtail with the ignition on?

 

https://xjbikes.com/forums/threads/how-to-ignition-troubleshooting.21932/

Although one other thing I would check is, with the key off, disconnect the 2-pin plugs at the coils and then measure resistance from grey to chassis and orange to chassis. I would expect these two measurements to be similar, and to both be pretty high. If you find that orange to chassis is much lower, that's probably a bad TCI.

 

SQLGuy my readings are as follows.
With the key off.

Pig tail # 1 with the Gray wire reads = Gray is 0-Ohms and Red/Whits is 88-Ohms


Pig tail #2 with Orange wire reads= Orange is 1-Ohms and Red/White is 88-Ohms

What do you think?

 

coil with orange wire is on right side of bike as you sit on bike? so plugs 2 and 3 are not firing?
Have you looked at the spark plugs? are they all sooty and black? dry or wet?
or are the plugs new?
brands of plug BP7ES NGK or W22EP ND
How long have you had the bike ?
how old is the battery?

The Ultimate Relay, Switch, Sensor, and Diodes Guide
so you have ohmed out the ignition system and every thing measures to the specs listed below?
XJ650 models:
Pick-up coils:
1980-81 XJ650 Maxim and Midnight Maxim: 700 ohms +/- 20% = 560 ohms to 840 ohms acceptable range
Ignition Coils:
Primary side (input from main wiring harness):
2.5 ohms +/- 10% = 2.25 ohms - 2.75 ohms acceptable range

Secondary side (spark plug wires, without their end caps):
11K ohms +/- 20% = 8,800 ohms - 13,200 ohms acceptable range

Spark plug caps:
5K +/- 20% = 4,000 to 6,000 ohms per cap acceptable range

Spark plugs:
0 ohms per plug

if you can not find an issue with ignition components with a meter
you could try swapping spark plugs from cylinder 1 and 4 with 2 and 3 to see if the issue moves with the plugs. this will help eliminate the plugs or coils as the problem.

if problem stays where it is.
if your spark plug wires are long enough you can swap plug wires 1 and 4 with plug wires 2 and 3. also swap the primary connectors. see if the issue continues or moves, this may require switching the spark pplug caps to fit. if the caps are OEM look where the spark plug goes and you will see a slot that can be tightened with a screw driver , just snug them up if loose. oem caps have a replacable resistor inside .

 

I have done that and get the same amount of Volts on both pig tails.

 

XJ550H

The spark plugs are new and the right kind. The battery is new and according to the meter, it is good. I have had the bike for two days. Just bought it for $200. Thank you very much for the guid. I will work on that, hopefully later tonight.

 

I'm surprised by these... but I don't have an XJ TCI to compare with. I may try to compare on my Virago TCI. I would have expected very high resistance here, because you should be reading from the collectors of the coil drivers to ground, with the transistors unpowered.

 

Just to double-check: you did disconnect the 2-pin plugs before measuring from grey to chassis, and orange to chassis, right? And this measurement should have been from the harness side of the connector, not the coil side.

I just checked on the Virago, and it's basically infinity to chassis from the grey and orange wires at the coils, with the coils disconnected.

Can someone else measure their TCI? The easy thing there would be just to remove the plug at the TCI, and check for resistance between the terminals of the TCI that correspond to orange and black, and then grey and black.

 

I unplugged the coils. Set the meter to ohms. Touched one lead to the chassis then the other to the pig tail, coming from the back of the bike.

 

That sounds like a bad TCI to me. But I'm surprised you're getting spark from either channel in that case. Anyway, you can try swapping the two-pin connectors between the two coils and see if your spark switches to the other pair of plugs. If it does, that's more proof that your coil is good, and more evidence that your TCI may be bad.

 

I have and it does, I’m going to work on it a little more but in the case I have to get a new TCI. Any suggestions?

 

They should be high resistance, the above reading (the good channel) he may be saying open or infinity ohms??

 

measured the tci on the ignition coil side got 1.9M ohm to 2.05M ohm between tabs black to orange and black to gray. tested 4 units

3 of the 4 tested 2 M ohms on both tabs and 1 unit tested 1.9m ohm- 2.05 M ohm
or did you want the tabs for the pickup coils?

 

That's what I needed, and more what I expected. Thanks!

Yeah, I'd say CTD's TCI is bad.

 

I did the same test, gray was nothing and orange was 0.9. Thanks for the help y’all, saved me a lot of beating my head against the wall. One more question. Any suggestions on the best way to get a new TCI? I’m on a very tight budget so as of right now, the cheaper the better.

 

I thought there was one of the guys on here that repaired them - Rooster, maybe? It may just be the driver transistor that needs replaced. Worst case, if you want to send it to me, I could take a shot at repairing it. I haven't done one before, but if it's the driver output, and maybe its driver, I could that.

 

I could take a look at it also if you like - I believe I already have the recommended drive transistors if that is all that is wrong with it. I will send a PM