No spark on 2-3 coil

I've got my '84 XJ 750 almost put together. Tried to fire it up but it wouldn't go.

I tested the coils and 1-4 seems fine and gives a spark. However, the 2-3 coil doesn't spark.
I tested the resistance (not sure i'm doing it right) and got 3.2 ohms between the wires in the white connector on both coils. On the good coil when testing between the plug caps I got 22Kohm. On the 2-3 coil I was getting 800K!
I tried to replace the wires but they don't really want to screw into the coil. I pushed them in as much as I could and twisted but the wire doesn't want to grab the terminal (maybe the terminal screws are corroded?). When pushed in all the way i still get 800K resistance. Anyone can offer some tips on properly measuring the resistance? I assume I'll need to replace the coil but any other suggestions would be appreciated. Thanks.

 

wires are part of the coil pack if tou can remove the wires from coil measure the resistance at the connectors of the coil

the spark plug boots do unscrew and are resistive. you may just need to trim the cap end wire back a little to get to good wire

you also want to test the pickup coils resistance

 

this link has your specs at the bottom of the page
http://www.xjbikes.com/forums/threads/the-ultimate-relay-switch-sensor-and-diodes-guide.27543/

 

Thanks for the link bud. I'll check them again against the specs provided.

The page show that I should be using 10Kohm plug caps though. The ones that were on here previously were 5Kohm. Does that make a huge difference?

 

Only as it relates to the plug-end-to-plug-end resistance that you will see when measuring. The plug cap resistors play two roles: Reducing electromagnetic interference from being emitted (which can interfere with proper TCI function (and radios), and adjusting spark duration. Running 5K caps will be fine, and will not affect the ability for a good coil to produce spark.

 

I swapped out my coils for 81 Honda CB750 coils they measure same as stock coils , mount in same location as stock you only have to flip over. These have removable plug wires and best of all are plentiful and cheap on eBay ..mine runs fantastic my old coils were cracked .

 

Would you mind putting the year along with your advice about those coils? I believe you used the '79-83 style coil. The earlier CB750 coils do not have removable plug wires.

 

if you should have 10k caps and you have 5 k caps you could also use resistor plugs to get to 10 k.
the 10k caps are available from xj4ever ,logo in upper right of page
HCP13193SET2 Aftermarket NGK SPARK PLUG CAPS, set of 2.
$ 9.75
HCP13192SET2 Aftermarket NGK SPARK PLUG CAPS, set of 2.
$ 9.75
HCP13518SET4 Aftermarket spark plug threaded top stud ADAPTER NUTS, set of 4:
$ 3.75

I needed the adaptor nuts because my plugs do not have them.

bottom line is if you are in spec from cap to cap using the + or - of the specs you are ok
with 5 k caps and resistor plugs (5k) you refresh the resistance when you replace the plugs

 

Thanks for all the input. The good coil measured just over 12K at the wires, without the plug caps, so it's in spec. I'll have to see if I can get a better connection on the other coil and if not i'll consider getting the Honda coils jetfixer mentioned.

 

I pulled off both wires and tried cleaning the terminals up a bit with some brake cleaner and anti rust cleaner. Used a thicker copper wire to try to scrape the terminals. I wish they weren't so deep inside the coil. I jammed a new plug wire in, but all that work only got the resistance down to about 600K ohms. I guess I need a new coil.
Jetfixer, any idea if a newer Honda CB750 coil would work also? I can get a 1999 coil locally for cheap.

 

The coils I used are 1981 vintage , 1979-1983 will work . These are Hitachi coils and have replaceable plug wires the will mount on stock location , just have to flip them over . I had positive results immediately with these coils , smother idle was one , my stock coils were cracked . I had these coils from my 82 CB750 Custom and just wanted to see if they worked so far it is a big YES . I would recommend if you don't want to spend big money on Dyna coils or buying the stock coils from our bikes ( non replaceable wires..unless you route the out) This is a really good upgrade. Cheers

 

Here is a picture of one of the coils ..pictures are better

 

bring in your coil for size comparasion, then check out its ohms if they are in the yamaha spec you should be ok.
I would suggest replacing them as a set if you can