nwcmc(at)tiscali.co.uk Guest
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Posted: Sun Feb 18, 2007 2:13 am Post subject: Rotax carb rubber flanges |
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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 £100/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’t 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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