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os 91 fx knock/ping

Old 05-24-2003, 01:21 PM
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OzMo
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Default os 91 fx knock/ping

first of all THANKS!! WHAT A COOL SERVICE!!
OK I have one of the 91 fx powerhouses and it give my four star 60 unlimited vertical, but IT KNOCKS at lower throttle positions 1/4 to 1/3 . i have stopped flying this plane because i,m afraid to damage the motor. reliable experienced assistance was available for break in and setting the needle valve and low settings . we tried richening up the low setting but this caused it to load up and die. DEAD stick low over the pond was "fun"! i was careful to seal the needle valve assembly and fuel lines etc. and it runs fine except for the knock in my cruise rpm area, any sugestions. DSIP
Old 05-27-2003, 05:25 PM
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Bax
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Default os 91 fx knock/ping

David,

Many engines .91-sized and larger make a 'knocking' sound at low- to medium-throttle settings. We've investigated a lot of engines that make this sound, and could find nothing physical that could make the sound, and found no engines damaged as a result of it. We've concluded that it's an exhaust note, and can change with fuel type, exhaust system, propeller, and so on. Usually, it's just something to live with.

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