Well the verdict came in today, the Tach cable needed to be lubricated.
Problem solved. Thanks for all the feed back.


Charles

"att news group" wrote in message
...
I ran the plane again late this afternoon, after de-fouling the plugs by
leaning it out during run-up at 2300 RPM. It flew fine, I didn't notice
any vibration, nor were there any wild fluctuations on the tach, I flew it
about 20 minutes. I then did a couple of touch and goes at a nearby
airport. On the way back to my home base again I saw the RPM fluctuate and
I thought I detected a little roughness in the way the engine ran. There
certainly has been no corresponding fluctuation in engine noise with the
fluctuation in the Tachometer.

Thanks for everyone's suggestions, I am going to have my mechanic look at
it tomorrow. I'll let everyone know what he finds.

Charles Graef


"Kyle Boatright" wrote in message
...

"Mike Noel" wrote in message
...
I would open up the cowlings and look over the engine very thoroughly for
any obvious problems (cylinder cracks, loose spark plugs, loose spark
plug
wires etc.) then pull all of the plugs, make sure they are all in good
shape, clean and gap them and swap the bottom and top plugs if they all
appear serviceable. Be sure to torque to the correct specification when
reinstalling them (it's about 32 ft lbs for my Archer.) Also be sure to
clean the 'cigarettes' at the spark plug end of the spark plug wires
with
something like MEK to avoid arcing around the spark plug. Then I would
do a
quick run-up check and, if the problem persisted, ground the plane until
a
mechanic had found and fixed the problem.

If the engine sounded fine I can't imagine that the engine RPM was
actually
going up and down several hundred RPM. A bouncing RPM indication is
usually
caused by a tach cable in need of replacement.


Bingo. If the engine sounded right, I'm sure it was fine. A 50 rpm swing
is noticable. A couple of hundred rpm swing would be attention grabbing
in the "Hit hte NEAREST button on the GPS" kind of way.

KB