Hi Ferg,
Many thanks for the suggestion. I have checked for all possibilities of
leaking air and have found no evidence. I have found, however, a small
slither of silicone in one of the needle jets, that I hope will solve the
problem.
Best wishes,
William
----- Original Message -----
From: "Fergus Kyle" <VE3LVO@rac.ca>
Subject: Re: Europa-List: 912 Engine Problem - Request for help
>
>
> ----- Original Message -----
> From: "William Mills" <combined.merchants@virgin.net>
> To: <europa-list@matronics.com>
> Subject: Europa-List: 912 Engine Problem - Request for help
>
>
> <combined.merchants@virgin.net>
> |
> | 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,
> There are those better qualified than I to comment, but I seem
> to remember a message of midrange misfiring being caused (eventually) by a
> suction leak in the fuel lines - greater effect in cruise/low power, than
at
> high power - and ground idle unaffected.
> FWIW, the difficulty was in finding the leak, as no fuel drips, staining.
> Ferg
>
>
|