1981 XJ550 pickup coil testing?

Hey guys, trying to diagnose a non running XJ550 with no spark. I see that the resistance of the pickup coils should be 650ohms +- 10%. I tested with my ohm meter at the plug for the TCI. When I connect my leads to the orange and black wires, it quickly flashes 100 and something ohms the goes back to open. The grey and black do the same. Any ideas? does this mean they are bad? I read and watched some stuff on testing them but wasn't expecting this result, and I'm kind of new to electrical trouble-shooting.

 

Did you disconnect the connector from the tci?
is your meter set to the lowest setting to be able to read the 650 ohms? 2k ohms would be the setting
get a can of electrical spray cleaner and a tube of dielectric grease. clean all connectors you disconnect and grease them when reassembling them.
it would be best if you keep all your questions on your project in the same thread it will help us keep track of your testing, issues and progress.

 

I had both connectors disconnected from the TCI when I checked. I'll have to pick up some electrical cleaner and dielectric grease. Should I start a new thread for my project, or maybe edit this thread? Thanks man.

 

sorry confused you for the other new guy with a 550
just keep it all in this thread and things will be fine, if you just have a generic question you can post it in a seperate thread but if it is about things you need to fix or repair it is best if kept in one thread.
check your inbox

 

So what do ya think about my pickup coil tests? Do you think it's bad?

 

So first make sure you have the meter set correctly as XJ550H suggested. It would be unusual to have two bad pick-up coils, but certainly not impossible. If you are confident in the meter and the reading and they are both indeed open, then try checking each of the three wires to ground.

A no spark condition can be a number of things and you seem to be on the right track of checking the electrical components associated with the ignition system. You should also go ahead and ohm the ignition coil primaries at the TCI connector and then the ignition coil secondaries at the plug caps - 1 to 4 and 2 to 3.

The other issue that shows up is a disabled ignition system from a safety circuit fault. It is designed such that the ignition is only enabled if the bike is in neutral or the side stand is up. The side stand relay can be removed temporarily to isolate / troubleshoot an ignition system safety system fault.

And for your safety in bringing this old bike back to life be sure to read the link below, it is full of valuable information to make the bike reliable and safe:

http://www.xjbikes.com/forums/threads/the-information-overload-hour.27544/

 

the pickup coils both have 2 wires running from them the 2 black wires are crimped together under the insulation I would check that crimp it may be loose or failed

 

Yes, it was set just like that. I’m pretty good with a multimeter, just new to troubleshooting motorcycle electronics. The primary coils read about 3.9 ohms, which I believe is kind of high, the secondaries like 12000. I by-passed the kickstand switch. Haven’t check the TCI connectors, but I stripped a bit of insulation on the wires and read the pickup coils there so I wouldn’t be reading the connector.
Like I said, I always got the same result, it would flash 100 and something ohms then go open. That was on both pickup coils. I ordered a used set off the bay for like 15 bucks, should be in Monday.

 

I’ll check it, is that crimp under the side cover?

 

Ok, so I retested the pickup coils with a much better multimeter and got a different result. So much for my cheapy!! One reads 675 and one reads 558. Now I know that 558 is technically out of spec, but is that really bad enough to keep it from firing?

 

No, not likely, and even so at a minimum you should have spark on the one that reads correctly.

So some more background on what you have tested:

How are you checking for spark?

You checked the secondaries on the ignition coils, but what about the plug caps?

What is the condition of the battery? The XJ bikes will spin the motor with a weak battery but the lower voltage produces a very weak spark. The battery voltage level should be checked when the starter is engaged and should be above 9.5 volts, preferably a bit higher.

You mentioned you bypassed the side stand switch, but as mentioned earlier it is best to remove the side stand relay to eliminate the safety circuit as the reason for disabling the ignition circuit. On some XJ's you can also do this by disconnecting the B/W wire bullet connector that connects to the TCI if it is easily accessible.

And any more history on the bike; when did it last run, any carb work recently done, etc

 

Pick-up coils:
650 ohms +/- 20% = 520 ohms to 780 ohms acceptable range
it is not your pickup coils.

have you ohmed out the ignition coils and spark plug caps trimed back the spark plug wire a little to eliminate and corrosion