Hi All,
Has anyone experienced a similar problem and can anyone help with suggestions
please?
On recent flights I have experienced some irregular misfiring when descending
with
about quarter throttle and also the occasional hiccup in cruise, but on my
last flight the engine was running so roughly in the cruise I aborted the flight
and nursed it back home.
I carried out some tests on the way back. It ran very smoothly on full
throttle,
it ran very smoothly on closed throttle, but in between it ran very roughly.
I checked the ignition when running roughly, but there was no change on either
mag. I tried coarsening and fining the prop to see if it was rpm related,
but it wasn't. I changed to reserve tank, but no change. The carbs are well
balanced at tickover and the engine runs smoothly right down to 1500 rpm. The
fuel filters are clean. I can only assume that the problem is related to
carburation,
but find it difficult to believe that one can have a partial blockage,
or too much fuel with a needle jet in its mid range only. As tickover is
smooth and roughness stops in flight when descending with closed throttle, I can
only assume that the slow running mixture adjustment and associated jet are
OK. Are there any other jets apart from the main needle and slow running jet
to consider? Although I never have a problem with starting, can a problem with
the starting carb affect the mid range running only? Can a faulty float valve
affect mid range only? My engine has done about 480 hrs, should I be
considering
renewing any of the carb parts as a precaution / planned maintenance etc?
I have had a brief chat with Conrad, but he was unable to put his finger
on the problem, so presumably my symptoms are unusual. He suggested I should
check the needles for wear and the carb rubber mounts / sleeves for splits,
which
I will.
Many thanks for any help,
Regards,
William
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