Most of these concerns are related to less than optimal set up by the
user and are not the direct fault of Rotax. I would make the following
comments about each topic raised.
>Cooling, Evans coolant or not.<
Provided adequate airflow is available through the radiators, the
standard 50% water/glycol mix is fine. For the Europa application in
very hot climates improved airflow can be achieved using a lowering
inlet chin flap. This can also be raised to reduce flow in winter to
prevent overcooling.
>The Ducati regulator. Italian electrics are grim IMHO when fitted to
bikes
,cars, tractors and it seems aircraft too.<
Whilst the Ducati regulator is not the most robust unit recent
discussion on the forum suggests that reliability is much improved if
the mean current load is less than 12A. Also improved cooling using
ducting is likely to improve reliability as well. Some failures are
caused by inadequate grounding of the regulator case.
>Sprag clutch or Starter motor.<
This has mainly been a problem associated with the 912S. The sprag
clutch wear was caused by kickbacks, which in turn was caused by the
higher compression of the 912S. A combination of using the higher power
starter and making sure the ignition timing is not too advanced seems to
have addressed the problem.
>Carb balancing setup.<
Any twin carb setup will need setting up correctly. Most Rotax users
manage to find a setting which achieves adequate balance.
>Throttle cables, are bowden cables best?<
Bowden cables give flexibility for various installations. There have
been a few problems where they have not been routed as smoothly as
necessary. Perhaps more exacting guidance of routing would help some
builders but avoiding tight curves usually gives good results.
>Crancase cracks!!!<
This has only just come to our attention. How much of a problem this is
as a percentage of all Rotax engines has yet to be seen. However the
fact that so many engine hours have been achieved before this has come
up infers it is likely only to affect a few engines. In any event it is
unlikely to be a problem with future engines as I am sure Rotax will
modify new castings accordingly.
>Carb mounting rubbers splits<
Any rubber parts are going to have a life and these are normally changed
as a service item at the 5 year point. The combination of high under
cowl temperatures and vibration means that this has to be considered an
acceptable requirement.
>Exhaust fractures<
This has come up a few times with certain batches of exhausts. Whilst
unsatisfactory this is not a problem which can be blamed on Rotax. The
exhaust manufacturer is employed by Europa and lessons have been learnt.
Part of the problem was associated with the fact that at least 3
different exhaust manufacturers had been used in the early days and
different exhausts used by the Classic and the XS. I am not aware of any
new problems that have not been fully sorted out.
>Hot starting,- fuel cooling required.<
This is one area which is made worse by the design of the Rotax. The
combination of miserly fuel flows and the fuel hose traversing the
length of the engine twice before reaching the carbs means that the fuel
gets heated within the engine compartment. This was the reason for the
bleedback pipe. Hot starts are a common problem with all closely cowled
engines. After shutdown the lack of airflow and fuel flow means the fuel
temperature easily exceeds 40degC within 10 minutes. Leaving the
inspection hatches open on short turnarounds helps but don't forget to
shut them again. I use the 914 NACA duct on the lower cowl for my 912S
to cool the fuel piping in the engine compartment using 50mm hose. As
this keeps the fuel temperature around ambient with the engine running I
have no problems with hot starts even without the bleedback pipe.
Nigel Charles
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