rwright142

I only flew once and the plane flew fine.
Engine was strong, sounded good, light smoke from exhaust, smooth transition from idle to full.
It is an OS FS 52 burning 15% Nitro and 18% synthetic oil.
I landed and was going to refuel for another flight when I noticed the liquid.
What is it?
I'm not a motorhead so I will not be able to tear it down, grab my micrometer, and let you know if the flux capacitor is in spec.
So, the question is, how much is this going to cost me?
Seriously, should I send it in for repair or is this something that I can beg a guy at the field to do while I watch and learn?

Thanks.

alan0899

G'day Mate,
Shove a piece of fuel tube over the vent tube, it exits the engine just behind the front bearing, & run it out the bottom of the plane, & support it somehow, clean the engine & plane, then fly it again, I'm sure you will find all will be much cleaner.
But the colour of that stuff is a worry, looks like aluminium rubbing on something, check & make sure everything is tight, muffler, carby, engine bolts, etc.

RussianFlyer

I'm no expert in four stroke engines, but from what I've read about them, that nipple on the bottom of the crankcase needs to have a tube connected to it and routed to the bottom of the plane. The oil collects in the crankcase and is expelled through the nipple...and into your engine compartment. The color of the oil may be from contamination/carbon. Smear some on your finger and look for fine metal particles. If non are found, you are probably alright and just need to route the oil drain properly. Just my $.02

P.S.: If the engine is new, you may find this kind of residue because parts are still breaking in and fine metal particles are carried out by the oil.

Ed Smith

If that black sludge is coming out of any engine during break in then there are major problems. Break in Does not involve ANY METAL REMOVAL.

Something is rubbing/vibrating together. It could be just on the outside of the engine, muffler/carb/motor mount etc etc. then mixing with the residue from the vent nipple. Claen it all up, as has been suggested put a piece of tubing on the vent and try again keeping a close watch to see if any more sludge appears.

Ed S

rwright142

Sorry, I should have noted this was NOT a new engine. It was flown for years before I got it and I have flown it for about 2yrs.

Everything is tight - carb, muffler, mounting bolts. Thanks for the tip on running a tube from the nipple out - I have added that and cleaned everything off.

Like alan0899 said, it's the color that is a concern. Why black? My first thought was that the black plastic motor mount was disintegrating, being rubbed, etc but all is fine there. I'm just worred that the inside of the engine is getting chewed up by a grain of sand, dirt, etc and it's eating the cylinder wall. Turning the prop by had seems normal - compression, no scraping or grinding noises, etc

The top of the engine is clean, and the prop/spinner areas are too.

exeter_acres

My Feedback: (2)

too lean?

rwright142

I did the full throttle and nose up test and it picks up speed a bit. Quick transition from idle to full is quick. On the ground at full throttle I adjust the HS needle for max RPM.
Should I be testing another way?

Rodney

Recheck every bolt and screw. Odds are very great that there is one loose and you have aluminum rubbing on aluminum (most likely external to the innards of the motor). from the looks of your picture, most probably one of the mounting bolts is slightly loose. It could also be the muffler to crankcase having some play; make sure the bolts holding the muffler to the engine are tight.

j.duncker

My Feedback: (2)

Yup looks like something is loose to me.

rwright142

Ok, thanks guys. I'll check again.
Muffler is tight on the engine and there is no liquid on the top of the engine.

jetranger-RCU

My Feedback: (1)

If there is no black on any other part of the engine but the bottom case most of the time the front bearing is loose in the case. This could be caused by a crash and the shaft could be bent a few thou out. After a while the vibes make the bearing wear in the houseing. Also WHAT is that string around the prop?? If you flew with that it could be rubbing against the front of the fuse and with oil could be the cause. If not see if you can wiggle the front shaft back and forth.

rwright142

The 'string' is a strap that is attached to the ceiling. I also have one wrapped around the aft part of the fuselage - just before the tail and the other I wrap around the front of the fuselage - the part that surrounds the engine - to hold the plane. The strap stays fixed to the ceiling - I don't fly with it on

I think the problem has been found. The engine mounting bolts have lock nylock nuts on them. My first inspection was wiggling the engine to see if the motor mount screws were loose then I wiggled the engine mount bolts and they did not move so I made the incorrect decision that they were tight. After testing their tightness with an allen wrench, all of them spun a little. So, can I assume they are tight enough to hold the engine on but were loose enough so that the vibration of the engine would cause them to spin - even a little - possibly chewing onto the motor mount? If so, then I can assume it is the cause of the black residue.
A test run produced no residue but I did not burn a full tank and was the run was on the ground. I will fly at my next opportunity and report back.

Thanks to all of the help!

j.duncker

My Feedback: (2)

Yup you found the cause and fixed it IMHO.

da Rock

You probably found the cause, but if you see it again after a flight, look for the following:

A lot of engines have a "windage washer" between their prop drive washer and the front of the engine. The drive washer is the piece on the prop shaft that your spinner backplate is tight against. The washer is usually very thin steel. It's purpose is to keep the drive washer from rubbing against the engine casing. And it's very easy for newbies to lose the sucker. Why do I tell you about this when you've not seen the goo return when running the engine just now? Because when the engine runs on the ground, the prop pulls all that junk that's bolted to the end of the prop shaft straight forward, away from the engine. Nothing rubs then. But when you fly the airplane and make turns and climb and dive, the prop experiences forces that cause rubbing.

If the front bearing is loose there will be enough play that with the washer missing, the drive washer can be "leaned" over and the rub the crankcase in flight.

Also, you said,
Testing? yes BUT...... that's not how you should adjust the needle. That's actually how NOT to adjust a needle.

First engine run of every outing, do this.
Start the sucker at a couple clicks over idle. Let it run at that leisure rpm as you clean up around the front of the airplane. Pull the glowplug igniter in that process but don't touch the engine for awhile.

The leisure rpm will warm up the engine with little wear or stress.

When you've got all the junk removed from in front of the airplane, move around back with your TX, get your hand on the needle and advance the TX throttle. When it's flatout, give the needle enough clicks TOWARD RICH that you know for sure the engine is too rich. That's one important goal.

Now click the needle toward lean until you hit max rpm. The next important goal is what this whole dissertation is about. Now give the engine a couple clicks toward rich.

How many clicks all these moves use is up to you. But the moves are important to the well being of the engine.

The short version of all this is fairly simple. You want to let the engine warm up gently. You want then to insure the needle is safely rich. Then you want to find the needle setting for max rpm on the ground. And finally, you want to insure that you don't fly at that setting, that the needle is set slightly rich from max ground rpm.
I got engines that I'd bet are older than you are. They all handle and run better'n new.

da Rock

Now, on the first flight, don't feel too smug about your needle setting. If you don't see exhaust in flight, you need to consider that the needle might still not be rich enough. Land the sucker and give the needle a couple of clicks rich and take off right away.

Our engines will give max power at settings most flyers consider too rich. You can tell about your engine/plane combination by flying it. It doesn't give it's best power when it's "dry lean". And it's aging fast when it's max rpm with no exhaust.

rwright142

Thanks for the suggestions.
What I normally do is let the engine warm up as you recommend.
I move the needed clockwise (CW) a click or two then wait a few seconds to hear any changes. If it slows down I move it counter clockwise (CCW). When I get max rpm (don't have a tach so I just listen for the change) I leave it there and then do my range check.

So if I understand you I should find the max rpm on the ground then move the needle about 2 clicks CW?

Thanks to everyone for your input!

Rodney

No, CCW, turn it slightly richer.

rwright142

Got it, thanks.

mscic-RCU

My Feedback: (6)

I would attach a piece of fuel tube to the nipple and check the color of the oil coming out of it. If the oil is black, then you have something wearing in the engine, most likely a bearing.

rwright142

Problem solved.
It was the motor mount bolts not being tight enough. On the ground they felt tight but would spin when the engine was running due to the vibration.
After tightening them up I flew twice yesterday. Each flight about 12 minutes. No black residue noticed.

Thanks for all the suggestions.