Hey guys. I'm running a os .40 fx and I had a few quick questions. I get some brown residue in the muffler and in the engine itself when I remove the back plate. It runs fine but I was just wondering what you guys think it might be. I don't think it's rust as I can see anything that looks like it's rusting.

The other question I had was about after run oil. What is that all about. I'm running 10% nitro fuel and I'm not sure of the oil content because I'm work. SHould I be using something different or something extra?

Thanx
Luc

lydo,

You don't say what brand of fuel you're running. That would help. An ABC/N engine like this one needs a standard fuel with a castor/synthetic oil mix. I can recommend Morgan's Omega.

The brown residue may be that's it not completely broken in yet. Or you may be running it too lean. If the residue is black or silvery, you're in trouble. That would indicate AL dust in the exhaust. That is a sign of parts rubbing somewhere in the engine. Also, if you rub the residue between your CLEAN fingers, you can feel any AL dust in it. The exhaust oil should be smooth to the feel.

Take the glow plug out and slowly rotate the crankshaft. If you feel ANY grittiness or roughness, the bearings are probably rusting. Replace them. If it rotates smoothly, there's probably no rust.

Dr.1

After run oil is just what the name implies. Oil that you put in the engine after you run it. You do this at the end of the flying day.
First pull the fuel line off the engine, install the starter battery and start/run the engine until it quits. This gets all of the nitro out of the engine which can be corrosive.
After this, remove all of the starting stuff and put about a teaspoon of after run oil in the wide open carb intake. Turn the plane over if you need to due to an inverted motor. Flip the prop through a few times to circulate the oil (do not use starter) and leave a nice coat of oil on the bearings and engine interior.

ATF (Automatic Transmission Fluid) can be used as after run oil and is much cheaper that the LHS. One quart will last a long time. Just put a little in a small bottle and take it to the field with you. First start the next time may be slightly smokey but it will be OK. There are other oil mixes that others will chime in here with, most are fine.

Some do, and some don't. Knock on wood, but I've never used after-run oil in 20+ years. Only had one engine to rust. It was a Como .40 that I left in the car trunk on a hot, humid summer night.

Dr.1

Actually, I don't use it either. I was just explaining what it was and how to use it. I've never had a problem in 30 years either. Of course, they will all lock up tonight. [:'(]

The most important part is to run the engine dry to get the nitro out. And I don't always do that either, but my engines don't sit long.

The brown residue certainly may be varnish, without seeing what your talking about, it's hard to say. Varnish is a naturally occuring biproduct of burning glow fuel. If this is waht it is, gon't worry about it.

I've used 3 in 1 oil and straight Marvel's Mystery Oil in the past. Lately, I've been using a 50-50 mixture of Marvel's Mystery Oil and Automatic Transmission Fluid. I think this is a good after run oil and I haven't had any problems with it. The problem with glow fuel is the alcohol, which attracts moisture and can start the steel parts in the engine rusting. Running the engine dry, as has been suggested, and putting a few drops of some type of after run oil helps alleiviate this problem. I put the drops in the carb, and bump the engine with my starter to disperse the oil through-out the engine.

And if stored inside in a climate controlled atmosphere, there's not much problem.

As you stated; all that bing said, they'll all rust up tonight. [8D]
Dr.1

I'm with the others in that I don't use the after run oil either. I always run the fuel out of my engine before I leave the flying field. Almost 10 years flying, so far so good, never had an engine go bad. So I guess the engine gremlins will visit me after Bruce and DR1 now!!!

Ken

If this was Friday, they would go to Ken's first. I knew I should have waited to respond.[:@]

Thanks for the replies guys. I would say the engine probably has about 3 to 4 full tanks of gas through it. Not more than that. The brown residue is very silky just like the fuel I put in to begin with but now it's brown.

The other thing I wanted to know... is it normal for the engine to spit out gas from the muffler?

Again because I'm at work I forget the name of the fuel I use, I know it's green but that's it. I'll check it when I get home and let you guys know.

One of the "green" brands is Cool Power. That is a good fuel. There are other "green" fuels too. As long as you have a commercial aircraft fuel with 10-15% nitro you should be fine. The Castor oil helps if you run too lean, otherwise IMO straight synthetic would also be fine. Too much Castor may gum up your motor. IMO

Yes, normal to spit out a little fuel/oil from the muffler. Especially since you are probably breaking in slightly rich. You just are not burning all of the fuel and of course much of the oil does not burn either. I would be more worried if it didn't spit some

The other question that I had was that if I take the glow plug out and turn the engine by hand I notice that when the engine gets to the top, it's hard to turn. Almost like the piston is hitting the head. If I slack the screws then it doesn't hit anymore. Is that normal as well?

Yes. This type of engine, when new especially, is VERY tight near the top of the cylinder (TDC). This will loosen up slightly as the engine breaks in. The loosening is part of what will eventually allow a slower reliable idle. This tight fit is also where some of the "coloring" you are seeing is coming from. The engines are machined to such tight tolerances these days on the CNC machines where they are made that they need to break in and "wear in" to a final fit.

I would not loosen the head screws (I'm assuming those are the ones you loosened, as you did not say). If you don't get the head back on perfectly straight and torque the head screws evenly, it is possible to distort the parts or cause a leak. I hope you are not moving the sleeve also while the head is loose

I did loosen the screws of the head and put them back in. I measured the torque before and after putting them back in. I do have tools for suck things as my father in-law is a machanic. I'm just new to glow engines so I had a few questions. I'll try and tune it properly this weekend and see what happens.

Thanks for the help guys.

I'm seeing the no oil guys winning this debate. Verrry interest-ink!

Well it wasn't really a debate. I had no idea what it was but I did read on this forum that people were using so I wanted that cleared up. Now it looks like I don't need it but I do know what it is and how to use it so it's all good.

No harm in oiling if done properly. Some fuels actually recommend against it though.
It's all a matter of opinion.

Why would you care what the fuel manufacturer's recommend. They don't own the engine. For 5-10 seconds the engine might have too much oil in it when it's first started. It circulates through the engine and is exhausted out and is gone until you stop for the day and add more. I haven't looked yet but will; what do the engine manufacturers say about after run oil?

The thinking on this may be regional. Most of the fliers I've hung with seem to do it. I won't argue with people whom don't do it and don't seem to have problems. However, I will continue to do so anyway!

Using ARO makes sense to me and I don't know anything. Logic tells me that little added protection will go a long way. Does WD-40 work as an ARO? It displaces water and protects against rust. Right?

Yes, WD-40 does displace water, and it does prevent rust. Its effectiveness as an after run oil has been widely debated. There are also reports that it somehow fowls glow plugs. There are probably better choices.

Thanks Chuck. Not sure why it would fowl a glow plug. Not like it will be in the cylinder for very long once started. It must be igniting to an extreme temperature over RC fuel? I will stick to my other options.

I have looked at the owners instructions for two Magnum 4 strokes, one O.S. 4 stroke and two O.S. two strokes. All five of these instructions recommend the use of either and "After Run Oil" or a light "Machine Oil", after use.

I think I might start using one. Better safe than sorry i guess. Plus the fact that running my engine right now at -15 degrees C. It's probably not a bad thing. I might try that trany oil thing. Seeing it smoke up at first could be kinda funny for people watching. I don't know why there aren't that many people in that kinda weather though...

Lydo, I believe the most critical point is running the engine dry after use. There is oil in your fuel and the fact this oil is so difficult to remove from your model when spuewed from the exhaust, gives testiment to the tenatious sticking/coating abilities of this lubricant. For me personally, I will continue to use an After Run Oil, as I know it doesn't hurt and it gives me a sense of security. However, you can trust the guys whom state they don't use it to have valid opinions, also.

If it contains any halogenated compounds it could poison the platinum catalyst. I don't know if there are any halogens present in WD-40.