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vbradley -> RE: is the fuel bad (11/26/2006 3:28:20 PM)
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OLD FUEL
Always be careful with fuel that's older than 12 months. Here's the lesson I learned. The local Hobby Town offered me a deal on some fuel that was about 6 months old. I used it for about a year. I was flying my 3D plane last summer and had a flameout which resulted in a severe crash. The plane broke in half. Engine not damaged, however I couldn't get it to tune up. It's a YS .91 and I've never had to tune it since initial break-in. Just replace the fuel diaphragm once a year or so. I even had the engine rebuilt at the factory in Nevada. The tech there said it runs fine, and he ran several tanks through it. It came back with the main needle open 1 1/8 turns. So now after the crash, I can't get it to run right. It's running lean, even with the main needle open 3 turns! Here's how I know it's lean: 1.) After about 1/4 tank, it stalls when advancing the throttle from idle, (which is exactly how it died when the crash occured). 2.) The engine is very hot after it dies. 3.) If left running full throttle, after about 1/4 tank the engine suddenly decides it wants to start running backwards.
Guess where the propellor goes at this point? RIGHT INTO YOU IF YOU'RE STANDING THERE! [:'(] Don't have it pointed accross the lawn, or you'll lose your prop nuts and washers. Do the tests on a concrete slab with the engine pointed toward a wall or fence.
Anyway, after reading a blurb here on RC-Universe, I learned that OLD FUEL get's thicker and causes the engine to run lean. It's a viscousity thing. In addition to that, fuel absorbs water from the air that we let into the can when we open it. So once it's opened, you should use it within a few months. Well, once I realized this, I got a fresh can of 30% nitro, and set the needle valve back to normal, then tested. Guess what? It ran two full tanks without even a sputter. My baby was back to running like new!
Bottom line on fuel: If you've got a favorite airplane that you DON'T want to crash or flameout (like a warbird or scale model) ALWAYS use fresh fuel!
Hope this saves someone a little pain![:@]
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