hilleyja

My Feedback: (3)

The oldest engine in my hanger and arguably the most dependable engine I have ever owned. She's starting to get a bit finicky lately. Once I used to be able to fire her up with a simple back-flip of the prop against compression (even when cold and not primed). Now that has become rare. She still fires up easily with a starter but her transition from idle to full is becoming less reliable -- she's bogging down on me, at least on the ground, after a period of idle -- I have to keep bouncing the throttle until she roars back to life. Bogging down in the air has not been a problem because she does not idle for more than a few seconds during any flight.

I'm running Wildcat Xtra Premium 15% (since she was new) and due to the castor content in the oil there is definite staining on the cylinder. When I pulled the head I found the staining is not due to leakage at the head but fuel bubbling from the carburetor blown back against a hot engine. Compression does not appear to be lessen and when I run her in the air she still turns heads mounted on my Sig Ultimate Fun Fly.

Bax, what can I do to restore her back to her once dependable self? Any suggestions would be appreciated. My estimate is that I have up-wards of 10 gallons of fuel through her over the last 3 years -- no maintenance, and minimal adjustments since new.

One of our club members suggested braking her down and clean the buid-up carbon from the piston head. How would I do that and is that a good suggestion?

Bax

My Feedback: (11)

Before you start to suspect a bad engine, though, make sure you have a good glowplug and that your fuel's nice and fresh. Water contamination can make the idle and acceleration go to pieces, with the engine tending to run hot at full throttle. You may also want to check out the fuel system to be sure it's OK. Since you mentioned that you've done little maintenance, the fuel system may need a look-see. Air leaks, damaged tubing, a clogged clunk, all of these things need to be checked. Also check the crud that may be in the bottom of the tank. Using a muffler for pressure lets exhaust oil get in the tank. Over time, you can get some sludge in the bottom of the tank. Your engine really doesn't like that stuff.

If the fuel, plug, and fuel system's up to snuff, then you need to check out the engine, itself. On a 10 oz. tank, 10 gallons' worth of fuel would be about 125 tanks' worth of running. It's possible that your engine is starting to lose compression. If the engine was getting tight from castor buildup, it would tend to run hot. When compression starts to go, idle and acceleration start to go.

If you want to clean the engine, disassemble it and clean it with an SOS pad and lots of water (the aluminum parts), or real soapy water and "0000" (four-oh, or four-ought) steel wool. Make sure none of the steel wool particles remain in the engine. Rinse under water as hot as you can stand to put your hand into, shake off and air dry. Oil and reassemble. You can dry the engine faster by rinsing the water off with denatured or rubbing alcohol.

If the engine runs even worse, then the piston/liner fit is going, and it's time for a new piston/liner assembly.

sgilkey

My Feedback: (180)

Bax, could you pls clarify, do you mean to use the 0000 steel wool to clean the castor buildup off the piston? or is this just for general cleaning of the outside of the engine? thanks.

Bax

My Feedback: (11)

You would use the 0000 steel wool to clean all parts of the engine, except the bearings, of course.

hilleyja

My Feedback: (3)

Well, I pulled the head and checked for carbon build-up. There was some but very little -- not enough to explain the engine's gradual lack of performance. I tried flying it this past weekend and now I have some damage on my Sig Ultimate FunFly that I need to fix. She was giving me fits during idle-to-full transition. I finally got her past the mid point and launched the airplane. That was a mistake; she deadstick as soon as she left the ground. I managed to get her down with only minor damage to the elevator.

I'm assuming my fuel system is ok because frankly its all out in the open (profile airplane) and easy to see if there are problems. I'm at a loss so I will be boxing her up and sending to Hobby Services for checkout/repair. I have another, almost brand new, 46 FX I will remount on the Ultimate.