912 excessive RPM drop on lane A

I haven’t read in the heavy maintenance Manuel about timing the prop along with spark plugs of a single cylinder so I’m sorry I questioned your sanity. I shared your post with a friend of mine whom I know is completely insane and he said your right on the money with the timing thing? he said he didn’t think    The 6-4-1 connector set up modules advanced. They just fire when the trigger coils tell them to. The yellow sticker on module reads 02 (year 2002)and doesn’t have soft start. How do I find out if they advance or not?

I agree that the older 6-4-1 modules to not have variable timing.

The soft-start feature Delays the spark until the engine comes up to idle speed; otherwise, the spar is always at the Advanced setting.

We are trying to find Something... Anything that will cause the problem to move/change/vary ... Anything!

We have eliminated the Spark Coil And Spark plugs.

Next would be to eliminate the Trigger Circuits by swapping the 4-pin plugs.  <---<<< This Next!

It would be ideal if you could borrow an Ignition module from somewhere to swap out the "A" Module with a known good one.

We may very well be barking up the wrong tree, but unless there is a better theory, this is all we have to go on.

I have switched the 4 and 6 pin plugs and in both cases I toggle b mag and lose 400 rpm  which tells me problem is associated with A. The only time problem is ever associated with B is if I switch the 1 pin plugs and that tells me my toggles are working correctly. I’ll buy a spare module if you think I need to go that direction but first I want to eliminate any concern of carburetor problems .

In as much as you already have the carbs in hand, You can test that theory first as the Ignition module will be a $900 Hard swallow.

One carb supplies Cylinders 1(A&B) and 3(A&B), the other Cylinders 2(A&B) and 4(A&B).

I can't imagine how a carb could possibly affect only one Ignition circuit.

Let us know the results. 

I know Bill, I have not flown in 6  months because of this problem. Don’t give up on me and the same with Garrett and the rest of rotaxowner family, the closest knowledgeable guy I know is 6 hours away.He says I’m not at the end of my rope yet but I’m pretty dam close. Between him and you guys I’ve been in good spirits and leaning a lot. At this point I could give a crud about 900 bucks, I guess a guy could always use spare parts for troubleshooting. I just want to fly. Thanks everybody,I’ll let you guys know what happens when I put the new carbs in.