Recently I pointed out that an alternative much cheaper source of carb
flanges was available. I have had input from a knowledgeable Rotax
service agent that non approved parts should not be recommended for use
on Rotax engines. I must point out that I am not making any
recommendation for this product. Normally I, like others, would be happy
to pay a bit extra to ensure that good quality parts are fitted. The oil
filter is a good example. The Rotax approved oil filter does cost a bit
more but it is a superior product and looks after the health of the
engine well. Although carb flanges only need replacing every 5 years, a
price of over =A3100/pair is excessive, hence the desire to find an
alternative. I understand that there have been a few cases of flanges
splitting over the years. In one case a flange failed after the first
start after it had been fitted. Rotax themselves indicate that there are
several reasons for failure even when the approved parts have been
fitted. In particular carb or prop imbalance, too low an idle speed,
loose engine mounts and poorly designed air intake systems have been
mentioned. With all these aspects on top of the choice of carb flange it
isn=92t easy to see what is the dominant reason for failure. I would
appreciate any information of instances of flange failure so that we can
try to detect whether there is a trend.
My opinion.
If the engine has been properly mounted with the carbs and prop balanced
and the idle speed set high enough then the air cleaner (or plenum
chamber) mounting and quality of carb flange might become the dominant
factors. A well mounted plenum chamber (as in the case of the Europa)
should give support to the rear of the carbs reducing the load on the
flanges. Carbs with directly mounted cone shaped air filters are likely
to put a greater load on the flanges. If the load on these flanges can
be kept low the chances of failure are likely to be reduced whichever
version is used. I emphasise this is a personal opinion and, as usual,
the final choice is up to the individual owner.
If I get enough information to show a trend I will publish it on the
forum.
Regards
Nigel Charles
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