912ULS Won't Start

I'm not going to be much help James, but FWIW on another thread here I just got some education from Bill regarding the spacing gap of those trigger coils ("4 little trigger do-dads mounted on the back appear to be solidly in place.") In short they not only have to be solidly in place but gapped right. 

I would assume/hope that the reputable shop didn't even touch those gaps, but if it's easy to check you might do that. Bill states the correct gap is ~0.4mm. Are they...the gaps... reachable?

 Throttle and choke positions?

The trigger coil gaps are not accessible with the engine mounted. I talked to the shop that replaced the ignition housing and he said they set the gaps properly. Throttle set at idle and choke fully ON, which is the way I always did it before. After no luck, I did try some other combinations.

I want to check if there is spark at the plugs. was planning to remove a couple of plugs, with wire attached, plug threads grounded against engine case, then turn it over with the starter and observe if a good spark occurs. Is there any harm in doing this to the ignition system??

Pull one plug each on a front and rear cylinder and do the hanging spark plug test.  No Harm!

Pull the 6-Pin connectors apart and re-seat them, they may not be fully seated.

And confirm the correct pairs are plugged together.  There are 24 ways they can go together, 23 of them are wrong!

Confirm the 2 Ground (Black) wires coming from two of the 6-Pin Connectors were Re-Grounded.

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And by "Ignition Housing", you mean that $1700 block of aluminum that makes up the whole back end of the engine. ???

The trigger coils spent at least a few minutes lying on a table before they were transfered into the new housiing and realigned.

This means that EVERYTHING related to spark generation is now suspect.

Thanks Bill, will do. Yes, the aluminum ignition housing was cracked. There was no new replacement in the US, so I opted for a $1400 used one that had been completely overhauled (yellow tagged) by an authorized Rotax rebuild center, with new water pump seals and new crankshaft bearing and seal. I agree, everything back there is now suspect. 

If your suggestions, which I will do, do not help, what do you suggest I do then? Completely dismount the engine again and ship it back to the shop in Arlington, WA that did the work? I feel plenty qualified to mount and dismount the engine and do all the hookups, but I don't feel qualified to inspect and repair the ignition system. I am resisting pulling the engine again due to all the work involved, two days to get it unhooked and dismounted, then 3 days to remount and hook up everything. Pulling off hoses that have been tightly clamped to barbed fittings is a REAL pain.