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I have a 1973 850 Commando that quits and has no spark. I was riding and the bikes was warm. New plugs installed. The Boyer has power. When you touch the box leads together you get spark. I snugged up all the spades on the coils. Coils had 3.4 ohms resistance. The resistance on the rotor plate were in spec. So not finding anything I put the tank on and it started. It wasn’t running properly as the timing needed setting. So the next day my buddy was over to help me set the timing and it quit when I revel the bike up to double check the the timing after tightening everything down. No spark again. Any help would be great. Thanks. Jeff

Jeff,
Very often this type of fault is caused by a defect in the cable which connects the stator plate to the black box. Most common is the point where the cable exits the timing cover ... repeated flexing causes the cable to fracture within the insulation.
The other problem area is where the wires solder to the stator's circuit board. Often the solder joint cracks.
.. Gregg

1. you don't declare the specific product you have, Boyer is a company brand. ( not that is matter that much...)
2. with most solid state ignition devices you have 3 failure modes, in additions there are various wiring malfunctions as Greg has pointed out.
3 the intenal trigger circuit can fail or go intermittant (rare)
4..WithIn the modules, the output transistor can fail in 3 fashions . Much more common.

A.In all cases it is basically heat related which manifest in mostly one of 3 ways.
B.The output transistor goes permanent short. Touching the leads makes a manual spark only.
C The output transistor is highly degraded and response becomes erratic as the box heats up, eventually goes into total short B
A variety of wiring connecting and trigger resetting does not yield reliable results

D Very rare is the transistor burns open and is totally non responsive and infinite resistance is open, no manual spark is possible.

Thanks for the help. It turned out to be a bad coil. Thanks Jeff

The new coil didn’t last a day. Can a Boyer me 3 kill a coil.

Just a Friday afternoon coil, I expect.

It's very odd that a new coil would fail suddenly. What failure did you observe... did the coil go:
- open circuit in the primary winding?
- short circuit in the primary winding?
- short circuit in the secondary (HT) winding?

What make of coil is it ? Is it a dual output coil, or two singles in series?

I wonder if the actual problem is a bad connection somewhere. Most common is in the harness feeding power to the Boyer, or in the kill switch. Also worth checking the cable that connects the pickup plate to the Black Box as I mentioned above. The cable tends to develop intermittent fractures where it passes through the timing chest, due to flexing.
Good luck
... Gregg