I would guess that one plug in the cylinder with the EGT fluctuation is
failing to fire and causing the EGT to jump when only the other fires. This
would also cause a slight loss of power as some of the still burning gasses
exit through the exhaust port for the affected cylinder. Perhaps this is
because the rings are still not seated well and oil is getting onto the
bottom plug for the new cylinder. If this is the case then it may go away
as the rings seat.

wrote in message
oups.com...
I am stumped as to what could be causing thing and am hoping someone
here can help me out.

A couple of flights ago I noticed that my EGT gauge started
fluctuating. Not fast but up and down a couple needle widths every
second or two. Then on the next flight I noticed that the tach has
started as well. Up and down 25 rpm or so.

I just had a cylinder overhauled about a hundred hours ago and I do
have have a much larger drop in the right mag that I need to clear to
get to normal on each flight.

My mechanic looked at my plugs last week and cleaned one he said that
had oil on it from the overhauled cylinder. I took it flying today to
see if that cleared the problem but it is still there.

Any ideas or thoughts?