After engine run routine maintenance

Use fuel with castor oil, and do nothing. It has worked for me for the past

-- Jim in NC

Run it dry at full throttle. Don't leave it in a place with uncontrolled temp and humidity. Worked for me for 25 years. Dr.1 Driver "There's a Hun in the sun!"

Run the fuel out of the engine so there's none left in the crank case. After you drain the tank, pull the fuel line off the carb and try and start the engine. If it starts, it will only run for a few seconds. If it won't start, just keep flicking the prop until it doesn't 'pop' anymore. I like to use After-Run oil in my 2-strokes (the stuff I've got is branded 'Hobbico'). Put several drops down the carb (try not to get it on any rubber bits like o-rings....I'm told it's not good for them for some reason) and flip the prop half a dozen times to make sure it works its way to the bearings etc. I store my engines so they aren't sitting nose-down.....anything left in the crank case will run to the back of the engine, instead of pooling in the bearings. Not sure if this makes any difference, but I figure it can't hurt :-)

MrBonk

Hi,

There are two elements that combine to make after-run maintenance a good idea. The alcohol in our fuel is hydroscopic (absorbs water from moisture in the air) and some acids are formed during the combustion process. Modern fuels contain additives that help reduce the acid products, and the lubricants do a much better job of producing a film on the internal components. From a technical point, the best of both worlds from the lubrication standpoint should be fuel that contains a mixture of synthetic lubricants and good old Castor. The synthetics should have superior "lubrication" qualities and the Castor fortifies the "oil" content during the high temperatures encountered in our small engines.

It is always a good practice to "run the engine dry" after the last flight of the day by pulling the fuel line while the engine is running at about 25% to 50% throttle. Then flip the prop through with the glow driver attached to get as much fuel out of the engine as possible.

Both our 4-C and 2-C engines rely on fuel/oil mixture in the crankcase to lubricate the internal components. With 2-C the fuel/oil enters the crankcase directly from the carb. With the 4-C engines, the fuel/oil mixture lubricates the internal components through piston "blow-by". Regradless of the engine type, there is oil and some fuel in the left in the crankcase after the run. The biggest down-side to this is that the moisture absorbed by the alcohol in the fuel tends to remain against the bearings after the alcohol has evaporated. The "run dry" procedure will remove a lot of the un-used fuel and reduce the probablility of corrosion. However, a good "after-run" oil can further decrease the possiblility of both corrosion and "gumming" of flight lubricants left in the case. The "gumming" problem is most evident with 100% Castor fuels in engines stored for long periods of time.

In humid climates, or seasons, the possibility of water corrosion is the worst. I currently live in an are where the humidity is very high 12 months out of the year and rarely below 90% during the summer months. Tools "rust" even when stored in "dry" garages. That is why I always use an "after-run" oil after the final flight of the day - even if I am going to fly the following day. In "dryer" climates, the problem is not so severe.

The commercially available "after-run" oils are good. But, are more expensive than "home-made". You can make a darn good after-run oil in larger quantities and for less money per ounce than the commercial stuff. Go to a good autoparts store and buy a can of "Marvel Mystery Oil" and a can of automotive transmission fluid. Mix the two components together 50/50 in a separate container that fits easily in your flight box. The best of the Marvel Mystery Oil product line for this application is their "air tool oil" because it is especially formulated to deal with the water that condenses out of the presurized air being fed to the tool. But, it tends to be more expensive and harder to find than the base product "Marvel Mystery Oil". The base product works just fine for our use.

I have been flooding my engines with this mixture as an after-run oil for over 30 years and I have never had a problem with corrosion on any of the steel parts and bearings. And, I have never had to tear down or soak an engine, that I have stored for years, to remove "gum" from oil flight oil.

I disconnect my fuel line, open the throttle, attach the glow driver, and give it a spin with my starter to burn out any fuel remaining in the engine. I remove the glow driver and put two or three drops of Marvel Air Tool Oil down the carb throat and spin it again. On 4-strokes, I run the oil down the crankcase pressure vent line.

-- Morris Lee snipped-for-privacy@verizon.net

Run it dry then add some after run oil -- I always use Marvel Air Tool Oil.

If you store the plane engine down, the after run oil can actually get to the bearings!

I would debate the assertion that there is any significant fuel left in the crankcase after the engine is shut down. The engine remains very warm for a long time and any fuel is completely vaporized. Add to that the fact that two stroke engines are open to the air unless you rotate the prop until the exhaust port is closed and leave it there.

More than likely the rust comes from garage storage of engines in humid climates where temperature swings cause expansion and contraction of the air inside the engine. This allows more moisture to collect. Engines in drier climates, like Arizona, tend to have almost no rust problems.

I left a Como .51 in the trunk of the car sitting in the driveway one summer night (after flying that day). The bearings were rusted the next morning. Since then, I've always stored my engines in a climate controlled room. No problems.

Dr.1 Driver "There's a Hun in the sun!"

That speaks of a metallurgy problem. I have bearings that have sat in my garage in the UK for three years with no signs of rust. These are bearings that were removed from various engines. No after run oil ever saw those bearings.

You guys are great Thanks for the advise!!!

Just out of curiosity, does your fuel contain some/all castor oil?

-- Jim in NC

My experience: for many years I did as Clarence Lee said, running the engine dry and adding "after-run" oil, and it seemed like I replaced bearings more often than anyone at my field. So, as an experiment, I stopped using the oil. I do run the engine dry, meaning I start it repeatedly until it won't even pop. I use fuel with 80/20 oil, so there is residual castor oil. After two years, haven't had any trouble with any of my engines. I live in a humid climate (SW Florida, near the Gulf). This may not make any sense, but that's what I have found.

The fuel I used was Powermaster 10% sport fuel. It has a small amount of castor, probably 2%. Most all sport fuels have some small amount of castor.

Where do you store you engines when not flying? I think that makes a lot more difference than anything else.

Can't do it with the helicopter (unless I hang it upside down from the ceiling by the skids!!). Mind you, leaving it sitting on the skids (crank facing straight up) didn't stop the bearings in *it* going rusty, although I suspect that had more to do with where it was being stored at the time (unsealed, non temp-controlled garage). I replaced 'em with stainless steel ones, so no more rust since :-)

MrBonk

Just how did those combustion gases get in the crankcase of a two stroke? Nada. The acid you are refering to is nitric acid and reacts with other combustion by products immediately and you have to be running over 80% nitro to have any substantial amount.

This is my experiance also. After run oil, rusted bearings, no after run oil, rusted bearings.

The only after run oil that works is castor oil. That is because the petroleum oil does not mix with water and floats on top of it. The water with disolved air then rusts your bearings. Also, don't store the engine nose down, water is heavier than oil and the water droplets will work their way down into the bearings.