rough mid-range and carb questions

Well, after all the contortions required to adjust those trigger coils, I have them all within 0.016-0.020.  I had just enough of a break in the rain to pull it out, and I almost wish I hadn't.  No change whatsoever.  This is really getting old. 

When I got home, I tested the CarbMate with a MityVac.  I used a T to connect the vacuum to both sides of the CarbMate, and it was rock solid.  The old MityVac leaks a bit, which was good. As the vacuum was being slowly lost, I was able to kink each of the CarbMate hoses one at a time to verify that it did move the indicator.  The only way this could be a sync problem now is if there's a vacuum leak on one intake or the other.  I guess I'll look into that, but since the carbs were rebuilt, and there are all new o-rings on the intake, there aren't a lot of places to leak. 

Might be time to call Ronnie at South MS Light Aircraft. 

Rusty

could it be worth a try, to eliminate it completely, to adjust throttle cables with engine running in rough area and see if roughness can be adjusted away ?    Without vacuum gause, with balancing tube in place and someone on the brakes.  

That's one of the tests I was planning to try today, assuming the rain stops long enough.  For sync operations, I usually tie a string to one of he throttle levers and run that back to the cockpit.  From the cockpit, I can pull the string to see if that moves the CarbMate indication the right way, or the wrong way.  That lets me know which way to adjust.  Today, I was planning to tie a string to both and see if I can make it smooth by pulling either. 

If this was a car, I'd try the old trick of spraying carb cleaner at the potential vacuum leak locations.  I think the prop would likely create too much wind for that to be completely effective, plus I fear that it would blow the cleaner back on the canopy and likely ruin it.  A safer method of leak detection might be to come up with a way to add some air pressure to the intake, then spray soapy water around the joints.  

The AFR unit will finally arrive today, so I can work on getting that set up for temporary use.  I'm even thinking of ordering an 8ch USB oscilloscope to be able to prove whether ignition pulses are happening as expected.  One way or another, I'll figure this out.

Rusty

Another unsatisfying day of troubleshooting. Testing the sync by pulling back on each carb didn't really help.  At one point I thought it did, but it was just because it lowered the RPM.  If you advanced the throttle enough to get back to the original RPM with that carb pulled, it was just as rough as before. 

The South MS Rotax guys didn't have much to offer over what I've already done.  The only thing they mentioned is a possible stator problem with power to the ignition modules.  They said they've had bad stators that did this, even though they had the proper resistance and no visible issues.  Mine of course measure exactly what they should, and no amount of flexing wires makes that change.  

Is there any alternate method of powering the ignition modules?  I may have to scope the stator outputs to see what the signal is, and also to see if it's being lost. 

Rusty

Compression tested good (even with new engine)  ?

Can you identify if one cylinder is not running same as the others by looking at spark plugs ? 

I used IR camera or thermometer to look for variations in header/head temperatures before

Magnet check with identical RPM drop ?   

Engine mounts and or cradle ?

test with other ignition modules, other coils and leads but this should be visible on magnet check

Propeller