hello friends.yesterday my engine explode while idling(broke the shaft).after 20 seconds of running suddenly exploded(not overheated).i use for fuel, optifuel 12%nitro ,oil 18% for 2 stroke engines.os suggest 20% oil fuel.i do not think it was the 2% of oil difference that made this.i bought the engine new but from other person(not from shop).i used only 1 galon of fuel when this happened.the engine was almost new.i notice before the last flight some drops of fuel on the backplate(makes the airoplane very dirty).also the breath nipple tube was black(in the previous flights was clean).the engine could not keep good iddle.i use 12x5 prop.the airoplane piper cub 2.5 kg.i did not push the engine.i flew slow.i do not know what is the reason.it was my first fs engine.is it so sensitive this engine?it was the bad fuel(it was not for four stoke engine)?bad tunning?failure from the manufacture?what do you think(not make the same mistakes again)?

looks like alot of rust on the bearings and cam gears

Looks like the rust caused a bearing seizure and sudden stoppage. Was the engine stored for a long time, say over the winter without after run oil. Do you live in a humid area? All can cause rust and from what you discribe there was a lot of rust galling the ring/piston on the previous run. I saw this happen to an OS 160, improper storage took out the piston and liner, the bearings were totally rusted and then filled the engine with rust when ran. Cost $190.00 to fix properly( I did the work). Was it bench ran before you purchased it, somehow it sat for a long time with fuel left in it.....your fuel is not the problem.

thanks for the answers.i have this engine only two months.i was told that it was new.the sure thing is that the previous owner had this for 10 years sitting.maybe he run it one time and leave it inside the box with fuel.is it possible so much rust for two months?i did not use after run oil.maybe it was rust before me.the piston is very clean.i do not know.i worry , cause i have already ordered another one without breathe nipple(os 72a).

Looking at the piston sleeve the engine doesn't look new. I see some piting on the piston and massive rust on the bearings. Usually a engine doesn't rust up like that with in 2 months unless you live in a very humid climate. Moisture can cause that kind of rust, but not like that unless the engine was submerged in water or left outside in the rain with no lubrication what so ever. I use Mystery Oil or After Run Oil if the plane is going to be stored for more than 3 months.

Did that engine come off a R/C boat or Float Plane?

Sorry about your engine. You might be able to E-bay those parts you need, might be cheaper that way than to order your parts from Tower or O.S. I have a mint condition 1984 O.S. FA 120 - Before Surpass ( Looks like a Saito). I still can get the internal parts for it, but if I damage the case like you did, I would have to look in the swap ads or E-bay for it.


Pete

Hi I am the MD of OPTIFUEL and came across your photos. The photos tell it all really, massive rust issues which I suspect seized the bearings hence the failure. OS recommend 18 to 20% synthetic oil. W use only KLOTZ products in our fuel which is known to be the world leader in synthetic oils for mixing with Methanol and Nitromethane. The oil has incorporated rust inhibitors in it but these are not designed to stop rust forrming if fuel is left in the engine.

Irather supect that this engine has had unsed fuel left in it and this has damaged all the carbon parts leading to a catostophic failure. Extract from typical OS manual. 18 to 20% oil and engines are delivered with needles set to 15% nitro with 20% oil.

<hr />
<font size="1" face="Helvetica"><font size="1" face="Helvetica"><p align="left"><span style="font-size: larger">The FS -56 should be operated on a methanol based fuel containing not less than 18% (volumetric) castor oil,or a top quality synthetic lubricant (or a mixture of both),plus a small percentage (5-20%) of nitromethane for improved flexibility and power. (The carburetor is adjusted a little on the rich side at the factory for a fuel containing 20% lubricant and 15% nitromethane.) Some commercial fuels also contain coloring additives as an aid to fuel level visibility. In some cases, these additives have indicated slightly negative effects on the performance.</span></p></font></font><span style="font-size: larger"><hr />We ship hundreds of thousands of litre of fuel per year and in Europe all the top Helicopter, fixed wing and car drivers run OPTIFUEL with very few issues. I think the engine you we sold as new must have had fuel left in it sadly and the result was terminal.

When you finish flying run the engine dry so it will not start, turn prop CC to compression and plug pipe with suitable bung. If the engine is left for any appreciable time use after run oil. Methanol is hydroscopic (will attract moisture) and if this occurs the methanol/moisture and nitro mix to make weak nitric acid and it is this that damages the carbon parts.

I hope this is of assitence.

Regards
Andy
</span>

I'm sorry about your experience with that engine. It certainly looks as if it was stored improperly for a long period of time. That being said, you will enjoy the .72a. It is a great new engine with a LOT of power for it's displacement. Follow the manual directions regarding props, fuel, break in and maintenance and you can't go wrong. I run 20% TOTAL oil in my 4-strokes with good success, at least a part of that being castor oil. I use many of the engines in float fly planes and never have I seen any rust. I am guessing that Athens is fairly humid and, having lived in Lisbon for several years, I'd encourage you to use the high oil content and be sure to run your engines dry after every session.
Best of luck over there.

All good advice in this thread.

My ritual every 6 or so months is to take the engine out of the plane, remove the exhaust, the glow plug, prop. I then get a container and fill it with Marvel Mystery Oil. I then immerce the whole engine and exhaust in the container. I put in enough oil to just cover the engine. I let it sit 24 to 48 hours and occationally turn the crank and such on the engine to remove any gunk or dirt inside. I then take the engine out of the oil, let it drain, then just towel it off.

It keeps the engine casing looking like new and the insides look just as good as well. I have been doing this since 1984 and I have a few engines that are as old and have been cared for this way their whole life. I use the Marvel oil as an after-run oil as well.

Hope this helps somebody.

As an aside, Os has not offered the 48 Surpass in years. A Magnum/ASP 52 will be almost a direct drop and as much or more power.

It looks to me like the crank pin had a crack that had been there for some time.
If you look at the last pic, it looks (to me anyway ) like a crack had existed for some time. Look at how the crank pin broke off flush with the face of the throw.
From the 9 o' clock to the 2 o' clock (almost half way around ) it looks like there is rust in / on the fracture line.

Looks to me like plain 'ole parts failure...rust might have been a contributing factor, but not the cause. If the engine had been run lean, then detonation might have caused the crack / breakage? The glow plug element looks frosted...that could be another clue?

The cam bearings are rather rusty, yes, but the rear main bearing and crank counterweight don't look all that bad. (I've seen MUCH worse )

gklept...does the rear bearing still rotate freely or is it rough or loose?

thanks for the answers folks.i will never buy again engine from other person(only from shop).that was my fault.i trust OS MAX.

I'll have to go with proptop on this one, that crankpin looks to have been cracked almost halfway through when you got the engine. You just happened to be the lucky one running it when it let go. Don't blame the seller too much, there is no way he could have known about the crack. I have a couple of OS 2- strokes (a 70 and and a 90) that look just like yours (or even worse)on the inside and they have been running for years with no problem. The 70 Surpass is just now beginning to feel a little scratchy when turned over carefully by hand. I will replace the crankshaft bearings before next flying season.

You will be happy with the OS (72) you ordered

I feel sorry for your "loss" []

Yeah it definitely looks like the crank pin let go. I can see the same thing that proptop was talking about with the rust build up. Funny thing is when the NTSB is doing a full size aircraft accident investigation that is one of the things they lok for when mechanical failure is suspected. One of the few things I remember from a college class I took a "few" years ago. I also have a motor, a Thunder Tiger Pro .46, that has over 25 gallons through it with bearings that look similar to those pictured. It still turns free and runs fine. It could use a new set of bearings but I am not sure it worth spending the money are a motor with that much time on it.

Looking at photo #2 I can see traces of red silicone rubber sealant. So this engine was at one time disassembled, and then reassembled using the silicone seal which is not the way it comes from the OS factory. This person sold you a used engine that had been taken apart for some reason.

To administrator: please move the post in the"glow engines" post.it is my fault

Next time if there is a next time, ask the person selling the engine to pop off the back cover and give you a good close up picture before you buy, it could help.