My OS 40LA seized up this weekend while I was starting it. It felt like it had ingested a piece of wood because I could still prop it over by hand but it was tight tight tight at the top. Today I took it apart expecting to find something in the cylinder and found it to be clear of debris but it was gummed up. The top of the piston is sooty where as the sides , especially near the top, are coated with a black varnishy residue. Now, I know this has something to do with fuels and lean/rich settings....but I have been flying the same type 15% Castor based fuel for about 2 years and the same needle set for 4 previous flights that day. What do you suppose got into this engine?
What is a good way to clean the residue from the parts.... I surely don't want to polish the piston or liner clean because this would change the tolerances. By the way, the crankcase area...rod crank etc is spotless.

Hmm.... I know alot of the time metal to metal Vibration causes that black stuff.. Maybe somthing loose in your engine? Or a bearing seized?[&:]

If you have been running an all castor or high percentage castor you may just be gummed up like you suspect. You could give the piston and liner a warm anti-freeze bath and that will clean off all the varnish/gummed/castor. I have seen this before on older engines that were run with an all castor fuel. With the anti-freeze bath no scrubbing will be required but I have had to leave parts in the mix for over 24 hrs a few times to get them clean. If you have questions just e-mail me.
Fred

Not too hot with the anitifreeze, though. I learned that the hard way. The ethylene glycol with evaporate very quickly as it heats up, and you'll be left with a black sludge residue that you'll have to clean out of your engine. Lucky for me it was just a muffler. I couldn't imagine trying to clean all of that stuff out of the intake ports!

Sounds like you might have hydrolocked the motor. Too much fuel in the cylinder, and it won't turn over. Forcing it is NEVER the answer--no matter what. If it won't turn over, DO NOT FORCE IT. There is something wrong. Unless you enjoy buying engines, you need to heed this advice!

BTW,
Piston heads are going to have a funky color to them--imagine all the abuse they take. Brown varnish is normal, and indicates burned castor. Black stuff, however, usually indicates aluminum shavings.

I agree with 2slow2matter it sounds like a hydrolock on the motor. I had it happen yesterday with my OS 46la. Tip the plane up on over and let the fuel run out of the muffler. Then remove the glow plug and then turn it over but stand back. The fuel will come out of the glow plug hole. Then put the plug back in and give it a try.

I suspect that the castor oil gum really is the culprit. If it was hydro locked it wolud have cleared very easily with no lasting effects (unless the con-rod bent).

Simmer it in antifreeze for ~12 hrs -- the goo will either be melted away or it will just brush off. The engine should be just fine after that.


The use of castor with ABC/N engines is a very good idea, as it helps protect against lean-run damage, & in the case of bushing engines like yours, it provides better lubrication of the crankshaft & shaft bushing. A periodic clean-up is a small price to pay.

Noticed in the owner's manual that OS recommends 20% castor. Jim

When you're running fuels with castor oil as a major part of the lubrication package, you're going to get some of it cooked onto the engine's parts. It's normal. Eventually, enough of the residue will build up to the point that it impedes the engine's running. Therefore, you have to clean the engine from time-to-time.

The anti-freeze system works well. You use an old crock-pot on the 'low' setting. Disassemble the engine and soak the parts overnight. This must be done in a well-ventilated area, and not in the house. You don't want to breathe the fumes.

Another way to clean the engine is to use hot, soapy water (dish detergent is good), and scrub all the parts with four-ought ('0000') steel wool. You can even use an SOS pad. Rinse in water as hot as you can stand with the bare hands, shake off, air dry, lube, and reassemble.

The color of the residue you find on the top of the piston or in the cylinder head depends upon how the engine was run. If it was on the rich side, you can most certainly get a black carbon buildup. Some of it may be soft and flaky. It scrapes off very easily. Some may be hard and black. That's what the steel wool is for. Brown varnish is just castor that hasn't been cooked enough to carbonize.

The black residue that signifies metal particles coming from the engine is the oil residue that's emitted when the engine's running. If the oil coming from the muffler is black, and has minute shiny specks, then you're getting metal particles. The engine is 'eating' itself. If the oil is black, or very dark, and there are no metal particles in the exhaust, then it's likely just oil that's being 'cooked' in the muffler, which does retain heat. There's more than just the color of the residue involved.

Thanks for stepping in Bill. You have officially heard it from "The Man!". Always appreciate your advice here.

Ken

You guys may think I'm crazy, but my 1/2a engines get cleaned with handcleaner. Goop or the other brands all work very well. All are ran on 35% nitro with 22% castor. You can imagine the nasty mess that I end up with!