No Spark - '82 XJ 650 Maxim

I have a 1982 XJ 650 Maxim that won't start. It will turn over, but there is no spark on any of the cylinders. I have the Haynes manual for it and I've gone through all the steps in the "No Spark" diagnostics and they all seem to do okay (except one), which leaves me with a potentially bad TCI.

The one test that doesn't work is the ignition coil resistance - I am reading roughly double the expected resistance on both the primary and secondary coils on both, which seems unlikely (right?). The bike was running in '13 and '14, but sat since the end of '14.

I'm not too sure what to do with it - should I replace the ignition coils first, or go for the TCI? Or is there something else I should do?

 

Swapping the coils out is generally less expensive in my experience.

 

Quite unlikely that both coils fail at the same time. Did you remove the spark plug end caps ? They should be off when testing.
Most common cause for lost spark is a fault in the side sand safety circuit or relay. Low voltage at the TCI is another one caused by bad wiring plug connections and old fuse boxes.

 

^^^+1 check fuse block if original replace with blade type fuses recommended . I replaced both of my coils with 82 Honda CB750 coils , replaceable wires , mount in the same location , are cheap on ebay . Bike runs flawlessly with these. Another possibility is a weak battery.

 

@mlew Thanks for the advice,

- Just to be clear, the starter is working and the engine is turning over - if the side stand safety circuit was bad, wouldn't it prevent the engine from cranking all together?

- I did notice an issue with the fuses the last time I was working - I picked up a new bladed fuse box from the local auto store, but the design has all of the fuses sharing a common blade. I tested the resistance to ground on all four wires and they were all zero except the main 20A fuse, so I didn't feel comfortable using that holder (however, when the key is turned to run, the 20A fuse's resistance drops to zero). I've ordered a new one and it should be here tomorrow.

- By "end caps" you mean the right-angle boots that attach to the spark plugs, right? I unplugged them from the spark plugs, but I didn't disconnect the boots and wires from the ignition coils:

 

The sidestand safety circuit only cuts power to the TCI when the sidestand is down (or the switch is stuck in the down position) and the bike is in gear with the clutch released. The symptom for a faulty sidestand switch is a bike that stalls immediately when the clutch is released, or randomly when going over a bump.

The sidestand safety relay and the headlight relay can be swapped for one another (and this hapens far too often, but then that's how a lot of us have gotten cheap, non-running, bikes). This will lead to a no-spark condition. The headlight relay has a dab of yellow paint at the connector and is located under the left side cover below the voltage regulator. The Sidestand relay is under the tank and has a dab of blue paint.

He does mean the spark plug boots. The ones that the meter is shown attached to in the secondary coil test. They screw off. The plug wires are not (easily) removeable from the coils.
The resistors can corrode, or fail, and the ends of the wires can corrode; all of which will increase resistance leading to a weak/no spark and high resistance readings. There are retaining screws in the big end of the boot that hold the resistors in place. Remove them and clean the resistors and contacts, then reinstall.


Any fuse holder that you use will require seperate feeds for each fuse; you cannot use a common feed holder without significant rewiring of the bike.

 

@k-moe Thanks, that's a lot of good information I didn't know.

- I have been trying to start the bike with the center stand down in neutral. Would a faulty sidestand switch still cut power to the TCI in this state?

- I'll clean the boot connections next time I get the chance, should be in the next few days. I'm looking forward to seeing how that changes the readings, although that would only affect the secondary coil readings, right? The primary coils on both ICs were reading double the expected resistance as well.

- Thanks for the confirmation on the fuse box. I didn't think it was a good idea - now I'm glad I ordered a different one.

 

If the primaries were reading high then the coils are faulty and must be replaced. Jetfixer's advice on which coild to use is spot on, and the least expensive option.