spark plug caps and coil questions XJ650 Seca

working my way through this 82 Seca... it came to me non-running, no battery etc so I'm figuring things out as I go, finding things that look odd, but I don't really know if they are concerns or not!

Currently the engine is rebuilt but out of the frame, the front end is totally dismantled, and I'm working my way through the rest of the frame etc, cleaning, replacing as needed...

Right now I'm looking at the coils and spark plug caps and scratching my head...

I've removed them from the frame as with everything for cleaning and assessment and today is their turn...

I guess I should follow the testing procedures I've read about elsewhere in the forum to decide what is usable and what needs replacing, but I'm curious about what I'm looking at...

I have two different types of plug caps...3 of one type, 1 of another... presumably the odd one out is a service replacement? anyone seen either of these types? and which type should I be moving towards?

Also, the plug caps seems to be full of some sort of dried, solid, crusty stuff... I tried to get a picture of... is this the residue of some sort of grease that would have been applied years ago to improve contact or waterproofing?

and finally, the coil bodies have some cracks in them... is this critical? is it worth my testing them, or at this stage should they be replaced?

thanks!


and this is how she looks today!

 

My opinion:
If trying to do it on the cheap, you could test them and use what tests good and hope for the best.

But if you want to be confident in the reliability then it is an excellent time to put on new coils and wires, along with going to a non-resistor cap and resistor plugs.

 

The plug caps might clean up, and if they do, fine. Chances are they're simply a bit knackered though. That residue in them is likely the remants of somebody's attempt to waterproof them. Ignition systems dancing blue sparks in the wet darkness is a sight you don't forget.
As for the coils - ohm them out and see. If they test ok you could fill the cracks with epoxy and varnish them all over.
Personally, I'd junk the lot and fit a pair of Honda MT-08s with new copper-core HT cables and new caps.

 

The metal-encased plug caps are the optional "noise suppression" (RF interference) caps that were available on some models. That means they're 40+ years old, I'd suggest replacing them.

Coils should be checked for resistance separate from the caps.

Checking Factory Coils:

Factory Yamaha coils need to "see" a total load resistance on the secondary side (the "going-to-the-plugs" side of the coil) of around 20-30K ohms (ohms being a measure of electrical resistance). Electrical resistance depends on a number of factors: wire size, type of material, length of material, ambient temperature, etc. etc. All readings are specified at 70-F.

In any case, all factory XJ coils and wires combined---BUT WITHOUT THE CAPS OR PLUGS ATTACHED---have the following primary and secondary resistance ranges.


Forget watching any other video on u-tube, etc. about how to test dual-lead ignition coils; this is the only one that shows how to properly test both the primary circuit (from the wire harness) and the secondary circuit (the "plug wires" side of the coil).......with the spark plug caps removed. You can ignore the actual readings that he is showing....the specs for XJ bikes are shown below.....but the method that he shows for testing the secondary circuit is the correct procedure:

www.youtube.com/watch?v=I0TKybs6Rnw
(skip to 3:55 for the dual-lead coil)

or you can read all about it here:

www.xjbikes.com/forums/threads/how-to-test-ignition-coils-and-plug-caps.130696



For all XJ models except XJ700, XJ750-X, and XJ900 models:

Primary (input from TCI): 2.5 ohms +/- 10%
= 2.25 ohms - 2.75 ohms acceptable range

Secondary (output to spark plugs): 11K ohms +/- 20%
= 8,800 ohms - 13,200 ohms acceptable range

 

looks like new coils, wires, caps are the way to go!