I have reason to believe my 1993 Kitfox IV 912UL 998 hrs. muffler may have been repaired incorrectly leading to a rough running engine (straw grasping).

The previous owner welded a plate on the end of the muffler canister where the exhaust outlet is - I can only guess that it was to repair a cracking issue. When I was reinstalling the engine and muffler, I looked in the inlet holes and noticed that the baffle (tube with holes in it inside the canister) did not go to the end and was offset toward one side of the canister.

Has anyone had their muffler open to see how the baffle should be? Could the baffle location be causing this grief?

The carbs are synched an the engine will idle at about 1800 for about 30 secs before getting too rich and overflowing. It is rough through 2000-2800rpm even though the carbs stay synced and smooths out a bit at 3000. At 3000 the carbs do not overflow but you can hear the engine stumbling a bit. At any point, the engine will run on either ignition with about 100-150 rpm drop. Every time I check plugs, the rear cylinder plugs are light tan and the front cylinder plugs are totally covered in dry black soot. All the compressions are 78/80.

Previously I posted about overflowing carbs and thought I had resolved by installing a fuel pressure regulator (which I should not have to use) and running the fuel pressure at 3.5psi. I have since realized that the engine can vibrate but it cannot shake or it will surely overcome the floats and overflow.

I have checked and rebuilt carbs twice, checked ignition coil wire and grounds, changed plugs, sprinkled holy water, etc, until I am one step away from making someone a really good deal... - on a plane with one of the most tedious engines devised.

Any advice will be appreciated and considered.

Thanks,
Charles