Experimenter

April 2013

Experimenter is a magazine created by EAA for people who build airplanes. We will report on amateur-built aircraft as well as ultralights and other light aircraft.

Issue link: http://experimenter.epubxp.com/i/118927

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Un d e r t h e C o w l centerline of the propeller shaft? Too high, and oil can start to siphon from the oil tank, overfilling the crankcase when the engine stops; too low can let the lifters go flat or cause very noisy and expensive trouble. Look for coolant and oil leaks. Water pumps—anything with moving parts that go through the case—wear out, and their seals are usually the first indicators. Likewise, check external hoses and lines. Look near the fittings to see if there has been crushing, scratching, or other abuse. How old is the engine? Not just total hours or hours since "rebuild," but total months since new? Oft-overlooked maintenance includes routine replacement of parts, regardless of use. For example, Rotax recommends a five-year replacement of everything rubber, from seals and lines to the carburetor boots. Likewise, five years for the fuel pump. (In experimental use, you may want to consider replacing the standard pump with a longer-life unit, such as the Billet pump and regulator). Disclaimer: The maker is a client of mine, but I shouldn't not mention it. It's a good and proven alternative. The Rotax four-bangers are finicky about what fluids are in their systems. Everything matters: fuel, oil, and coolant. They can use 100LL, but prefer unleaded premium, nonethanol auto fuel. A diet of 100LL requires doubling oil changes and frequent cleaning of the oil swirl tank. 100LL leaves deposits that will eventually accrue inside the engine (see photo). Even momentary oil starvation can lead to a ruined cam and case. For experimental use, some shops will line-bore the case for replacement bearings; this fx is not permitted ofcially and cannot be used in certifcated or light-sport aircraf applications. Unleaded premium auto fuel that does not contain ethanol is difficult to find (links below), so many users simply burn enhanced fuels. Corn-fed fuels aren't as stable; over a very short time, they absorb water from the air. They also evaporate quicker (leaving a lower-octane fuel behind), and they tend to "sludge up" faster, making frequent flying a (pleasant) mandate. Again, the airframe logs will give you useful information. And knowing what fuel the engine has ingested is critical. Even the oil used in the (oiled-foam or K&N-style; pleated) air filter is prescribed. And the engine oil is critical—regular "aero" oils and automotive oils with "friction reducers" are not recommended. The Rotax-Owner.com website keeps an updated list of workable oils. The oil filter looks like an automotive unit, and many car-type filters will "fit." But only the Rotax unit will "work." Te right oil, clean and always available, will help prevent such expensive and dangerous destruction. 34 Vol.2 N o.4 / A pril 2013 While you're looking at the seller's shop, notice the parts cleaning tank and find out if he has used it to clean oil lines or coolers. If he has, he has introduced "swarf" into the system. The cleaning tank is full of destructive abrasive waste, and washing other components in the same tank can ruin engines. Filter or not, everything in the sump of that parts tank can potentially get into the engine's bearings. I'd go so far as

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