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fx 61 loosing power

Old 09-22-2003, 02:03 PM
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Default fx 61 loosing power

I have an fx61 i bought new this spring and have run maybe 3 gallons of 15% cool power through by now. A while back the stock muffler fell apart mid flight and i replaced it with a macs tuned pipe setup.

Not being a great tuner of pipes it did work ok but was running a bit hot with the os 8 plug and i switched to a cooler mccoy 9 plug. This helped out but i developed a head leak. I retorqued the head and then replaced the copper ring and still had leaks. I then put on a one piece aluminum macs muffler and still have the head leak. power is not impressive and im sure it has to do with the leak. Any thoughts or suggestions? Im running it with a 12x6 apc prop.

Thanks

Sean
Old 09-23-2003, 09:35 AM
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Default fx 61 loosing power

To my knowledge the FX series is more of a sport design and not really timed for a pipe.
I've put them on sport engines before with OK results, but really didn't gain the benefits of the pipe. Piped engines tend to run a little hotter and the needles get tweaky with a narrow tuning band at times. This in conjunction with the remote needle may have leaned your engine a bit and maybe you lost some compression. The head may or may not be warped? What spec did you torque it to, and was the engine cold when you did?
I just acquired a used plane with a .61FX and had to replace the carb with the old standby, a Perry Carb. It runs great now. Good luck and let me know how you make out_bob
Old 09-24-2003, 09:34 AM
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Default RE: fx 61 loosing power

From your description, your engine's had an overheat. That means that the tuned pipe system was likely on the short side and causing the engine to trend lean.

All tuned pipe systems need to be adjusted to suit the engine their used with. There is no such thing as a tuned pipe system you can just bolt on and expect to work. You have to spend time getting it tuned to the engine/propeller combination.

At this time, it's very possible that the cylinder head's been warped a bit from the overheat. You'll likely need to replace it and the head gasket. O.S. does not use copper or brass cylinder head gaskets. They're aluminum, and many people look at the cylinder head and don't see the gasket that's there and assume there is none. A very close look will reveal the normal gasket.
Old 09-25-2003, 06:34 AM
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Default RE: fx 61 loosing power

Thanks,

This was my first attempt at a pipe setup and i did leave it long as per macs website recomendations for that motor but i believe that the used pipe i was trying may have mis matched. I will check the head tonight for warp.

Sean

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