Please can someone suggest a cure for my rough running Rotax 912UL. The
symptoms manifest as a noticeable pulsed vibration, about once a minute,
through the airframe, joystick and rudder pedals about 15 minutes after
start-up ie within five minutes after take-off and when revs come back
under 5,000. It is as if she is trying to clear her throat and it is a
little less noticeable if the fuel pump is running. I was lucky enough
to acquire her (a Mono classic) quite recently (kit 33). I have tried
the following:- new regulator, new spark plugs (the old ones looked
perfect), ohms tested HT leads, pressured tested cylinders (virtually
identical), balanced the carbs., removed stripped and pressure blown
carbs, drained fuel tanks and refuelled with Super unleaded. In case it
is relevant I cruise her at 4,800 rpm, at 2,000ft amsl which gives
approx 118kts burning 14+lph. Today for the first time I refuelled with
Avgas and was surprised to find that above 5,000 rpm the engine ran like
a sewing machine and only tried to go back to her bad old ways at 4,600
rpm and below. Please could someone point me in the right direction -
Thanks, Bill Wynne
|