Had a rough running engine twice now and here is the scenario:
Another pilot friend flying my airplane had this
First event at level off@4200’(1200agl) at power reduction to cruise engine got rough and lost 2-300 rpm- corrected itself and did it again. Over airport so he landed uneventful. Troubleshot in the air carb heat-switched fuel tanks- then landed. Mechanic suggested a bad mag. Replaced mag with new. Run up fine.
Second event( next flight) with me flying.—cruisedat 4500’ for about 30 min with all normal- then same thing-rough and rpm loss. Troubleshot all the above plusmag check left off/on right off/on —-no change. This eliminated an ignition problem in my mind. Landed 15 minutes later and engine smoothed out in that timeframe.
I highly suspect an intermittent stuck valve???? I’m stuck in the field(AMA) and will have an A&P look at it tomorrow, but I don’t want to walk in there blind. Any ideas or suggestions?
Thanks Ted
Rough Engine
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Re: Rough Engine
It could be...
The first event was right after a power reduction: prime time for a stuck valve. The second one wasn't, but that doesn't prove anything. Unfortunately, unless you can catch it while it's stuck, it's tough to prove definitively. You can ream all 4 exhaust guides prophylactically, but there's not much else to do. Check the valve springs, too, while you're there.
You don't have a Marvel carb, do you? If so, check the venturi and, if you have the one piece venturi, see if the updated emulsion tube is installed.
The first event was right after a power reduction: prime time for a stuck valve. The second one wasn't, but that doesn't prove anything. Unfortunately, unless you can catch it while it's stuck, it's tough to prove definitively. You can ream all 4 exhaust guides prophylactically, but there's not much else to do. Check the valve springs, too, while you're there.
You don't have a Marvel carb, do you? If so, check the venturi and, if you have the one piece venturi, see if the updated emulsion tube is installed.
John Cooper
www.skyportservices.net
www.skyportservices.net
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Re: Rough Engine
I do have a Marvel Carb. I don’t have all the paperwork with me right now but I know the one piece Venturi was installed— don’t know about the emulsion tube?
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Re: Rough Engine
Im a complete rookie to these gals but was reading similiar stories in "live to tell" at backcountry pilot forum... several fouund issues w either small paint flakes in carb and one guy found fiberous material in his gascalator and figures it had come from someone filtering fuel through a chamee the wrong way... again take that for what it cost but it wasnt dissimilar occurances... i beleive the thread was called the sputter club or something to that effect...