Miss fire

Reasons for the AC voltage dropping:

1. Fault with the generator coils/magnets/mechanicals.

2. High resistance joint in the circuit resulting in a voltage drop under load.

3. Excessive load causing the voltage to drop.

I don't know how much power the ignition draws from the generator but I suspect that it isn't that high so there would have to be quite a high circuit resistance to cause a 50% voltage drop. This makes it seem quite unlikely that this is the cause.

I am intrigued by the fact that the problem only occurs at a precise temperature. I know that if magnets reach their Curie temperature then they lose their strength. For the flywheel magnets I think that this would be over 400°C.

Is there any way that there could be a problem with the ground connections of the generator coil? Is there any chance that something could be interrupting the ground from the flywheel housing to the ignition module grounds?

Where exactly are you measuring the AC voltage? i.e. where are the 2 connection points?

I think when you are completely stuck on a problem like this, you need to set aside everything you think you know from your investigation so far, and start afresh, if possible from a different direction. Otherwise you end up going round and round the same circle.

A good starting place would be to remove as many variables as possible. So I would:
1. Make sure you have 91 or better in the fuel system as per Rotax recommendations. (Also avoid 100LL if possible, but that is a separate story.)
2. Check the trigger coil gaps as suggested. We know that incorrectly gapped coils (both over and under) can produce strange results. Assuming you have the newer coils the gap is 12 to 16 thou, so 14 is good and not hard to do with brass feelers.               
3. Check the ignition modules ground wire. If you have the newer modules, this is Item 26 of Fig 74-25 in the Heavy Maintenance Manual and goes from the module mounting bolt to a bolt on top of the RH(?) inlet manifold. I would visually check the terminals on each end, and meter the wire for continuity.

If all that was in order and the problem remained I would next swap the Rotax modules back in. I would eventually do that anyway, unless one proved faulty. And the reason for that is that by swapping in a module, it is possible to introduce a new problem (if there is a problem with the swap in) and then you are troubleshooting not one but two problems.

With that done, I would run the engine in a minimum configuration: Disconnect one module (don't just turn it off), rope the aircraft to a
handy tree, partly blank off the oil cooler, and run the engine up to temp (obviously watching the oil temp carefully so as not to overheat).   
Then repeat with other module, if necessary.  

These are two completely separate systems, the only thing they share is the ground point (3 above).
So if they both still fail as you describe, that only leaves the plug leads and plugs. And if they're okay, it's not an ignition system problem..
                   

It has a completely separate charging circuit along with its own set of coils the ignition stator part is separate and is redundant the voltage for the charging circuit does not drop like the ignition voltage does. When I hook up the meters they are hooked directly to the ignition stator coils they operate at 30 volts AC at full rpm of course the voltage might go up or down according to rpm a bit but to drop down exactly half is weird to say the least. The fuel wouldn’t have any connection with it and all the grounds are good the after market ignition boxes have a feature to allow hooking up a switch and running it off a 12 volt battery source incase the stator were ever to go bad and that’s the way I found it was a drop in voltage then I hooked up the meters to verify that. The reason for the swap was because I obviously had this problem before because it was doing the same thing with the rotax ignition only I didn’t know what the problem the 12 volts directly into the ignition from the battery made me put the meters on it to verify and another reason to put the other boxes on is because they have a built in ignition timing for starting in cold weather,and I also put on the new flywheel that has the retard feature built into it but this was all happening before any of the new parts so when I get time I’m going to do some more checking. I’m going to first check the air gap on the trigger coils to make sure there all within specs but I can’t see where that would have anything to do with a loss of voltage,the only other thing would be to put a brand new stator in it this was a used one but worked flawlessly so that’s where I’m at. Thanks for the input and 195 is a little cool running for some of them,a lot of them run around 210 so I’m up for anything now but I’m busy farming right now so it’s on the back burner for awhile. Gives me something to think about while on the tractor! Lol