81 xj550 Can't get a spark

Recently purchased an 81 xj550 and started turning it into a cafe racer. Re-wired the entire bike and had a working harness and a running bike. I continued to wire the lights and blinkers and somewhere along that line I may have hooked up a test battery backwards accidently. Anyways finished all the wiring and now I can't get a spark. Ive got 12v at each coil pack. I've ohmed out all the spark plug caps and cables. I had a hard time getting a good reading on the regulator but did get some and I think its fine. I couldn't get any resistance through the pick-up coil. BASICALLY WHAT DID I FRY??? LIke I said the bike ran fine two weeks ago but now no spark. Before I start buying all new ignition system parts I want to know what would/ wouldn't fry. Thanks guys

 

Update: I measured 650 ohms through each pick up. When I measured the voltage at the coil pack leads on the TCI with the ignition on I was getting about 12.5 when I turned the motor the voltage would start dropping to about 9v after about 4 or 5 seconds of turning it. I don't have an analog meter to see oscillation. ANYONE HAVE ADVICE? Thinking its the TSI, does anyone on here rebuild or inspect them?

 

if your battery drops below 10 volts(9.8 volts) the tci will not fire
a place in england rebuilds them there is also a new zealand company selling them for about 200$ they are on ebay.

how old is the battery? sounds like a battery problem with it droping below 10 volts.
put a full charge onthe battery if you have a charger
hook a car battery to your battery with jumper cables do not start the car see if it fires up like that.

if you think the tci is bad have someone try it in thier bike for you.
I am testing another members tci this weekend hes from salt lake city too.

 

Where in SLC are you? As XJ550H said, he is testing my TCI unit to see it it's bad as I'm having the exact same issue as you are.

It's definitley a brain buster for sure. Maybe we can help each other out.

 

Thanks guys, if I remember right the battery stayed above 10v when cranking fully charged. I'll check again today and try a car battery. I have the bike actually up in Park City right now. But definitely down to collaborate jmcgrew. Also be nice to meet some other xj owners! I was going to get the bike safety inspected the other day and went to start and nothing. I'm so close on this bike haha.

 

did you ohm out the primary side of the ignition coils?

do you still have the airbox ?

 

Both coils read 2.6 ohms. Airbox is gone, pod filters installed with 4-1 exhaust

 

Just ran it with car battery. No spark but the battery ground cable started to smoke and melt...

 

Minimum wiring right now just to try and get the engine to turn. Starting relay just clicks and starter doesn't engage

 

Moved the battery ground from the frame to engine block(new ground wire). Motor turns but still no spark, Everything seems to be pointing to the TCI. Gonna order one up and go from there. jmcgrew have you been to bills boneyard in slc? Wondering if they have a TCI for an XJ

 

need ground on frame and motor.
the voltage reg grounds to frame at coil pack mounts.
the battery grounds to frame and motor
the pickup coils has a ground wire on the mounting plate not sure where this connects in the run through the harness but I will check on my spare harness

 

That might be the problem. Thank you!

 

I've never been to the Boneyard, but work just down the street.

 

Did you get your bike to start up?

 

Just got back into town. Got a new TCI, going to try that and redo the grounds. I'll keep you posted

 

Plugged the new TCI in today and I have spark again! Now to re-wire the harness again