Hi! Richard.
I'm not a Rotax "buff" but IMHO it sounds to me like a weak mixture case,
where you are lightening the load and get a rough run due to mixture. Whilst
in the climb you may have the carbs delivering more fuel that the engine can
develop power for , so when you throttle back the mixture leans off too far
giving a rough run.
Just a suggestion, perhaps some carb tuning specialist would care to put his
remarks to this theory.?
Regards
Bob Harrison G-PTAG Europa MKI/Jabiru 3300 (back in the air with a 200
re-ring job done...... bet you can't do a ROTAX 4 Cylinder as cheap !)
----- Original Message -----
From: "Richard" <riddon@btinternet.com>
Subject: Europa-List: Rough running 912S again
>
> Following my report of rough running of my 912S last week, I flew with
> my inspector today to try to replicate the conditions in which the rough
> running occurs.
>
> It seems to happen at the top of a climb, when the aircraft is levelled
> off, speed builds to cruise then I back off the throttle. At this point,
> the engine 'plucks' for a minute or so then smoothes off. I have a C.S.
> prop and if I keep the manifold pressure towards the top end of it's
> range, say 25in. the plucking continues until I back off the throttle
> and reduce the pressure.
>
> The day was rather cool and humid, the windows kept steaming up even
> with the vents open. Is this likely to be carb icing or does anyone with
> rather more experience than me have any other idea's?
>
> Richard Iddon. G-RIXS
>
>
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