So today at the field I was trying to crank up my OD 46 sized engine.
http://www3.towerhobbies.com/cgi-bin...XFMD5&P=ML

Immediately the engine started sputtering and it became stiff and the prop would not turn easily.

My instructor took a look at the engine and we found this :





He told me that my engine has run a bit lean and my piston was scratched.

I'm asking for any advanced pilot to help me fix this problem.

My instructor's suggestion was to buy a new piston:

http://www3.towerhobbies.com/cgi-bin...LXGCU6&P=Z

I am not willing to spend 76$ on this new part.

Is there like some solution I can use to fix it?

Or is there anything I can do?

If you want to buy it go ahead, because I am clueless of what to do...

You pretty much have two choices:

1- Buy a new engine
2- Replace the piston and sleeve. I would also look closely at the connecting rod bushings, crank pin and crank bearings. You'll also need new gaskets and o-rings.

As for the cause, I agree that it could have been run too lean. Fuel with too low of an oil content could also similar problems.

Generally, glow engines need to run slightly rich to make sure they stay cool and are well lubricated. Too often people try to squeeze every last RPM out of them. Do it once and you might just get a dead stick. Run it that way too much though and you'll end up with a serious failure like this.

It may still be under warranty?

Sometimes the OS will do this no matter how you ran it.

I'm not to sure what new engines cost there by you guys, but for the price of a new piston and sleeve you can just as well get a new engine and if you want to you can someday buy the parts over seperate months and fix the engine. That definitely looks like an engine which got run too lean.

Which model OS46 do you have? Check out JustEngines web site as they have some piston liner combos that fit some of the OS engines for a reasonable price after removing vat of 15%. Their service and price was good when I bought from them.

What about a decent used engine?  I recently saw a .46 sized O.S. engine on craigslist for $75, gift wrapped in a plane complete with Servo's!  You never know what you can find, and they are so easy to get apart you can easily pull the head off and look at it before you buy it, if the seller will let you (if they won't, I'd wonder what they were hiding and move on.)

Donle,

Contact the factory support: E-mail: [email protected]

Use your warranty; it is a AX, parts are precise and expensive.

Yes, you need to replace piston and sleeve, at least.

Start using fuels with a mix of syntetic and Castor oils, since they have better protection against what happened to your engine.

That scoring was caused by more than just the engine running "a bit lean".

Though the picture is very blurry, it appears that something fell into the combustion chamber and then lodged between the cylinder and wall.

Did you use a fuel filter between the tank and carb?

Did you filter the fuel when fueling the plane as well?


I've accidentally run engines hot and lean to the point of siezing, and the damage was not nearly as bad as that.

If anything I merely returned the engine after it cooled down, and started it right up again w/o any problems.

the piston and cylinder is the heart of the engine....$75 repair on a $135 engine isnt too bad....it was def run lean, and got hot at the exhaust port,..a good machinist might be able to repair it, but it would cost about the same....I'm guessing you bought it used so, you may need the original buyer to send it back, if its still under warrantee....Rog

Well, thanks.

1. Its an AX.
2. This is the best engine on the market for my sized plane.
3. I brought it new about 1 year ago.
4. I don't think anything lodged in there.

I will try emailing towerhobbies and OS because that is where I purchased them.

Thanks for help

That cylinder sleeve has peeling on the outside too which surly doesn't have anything to do with how you ran it.

Is this the notorious peeling nickel "plating" of the OS ABN/ABL engines? Which engines of OS were "plated" this way, and are any particularly bad for peeling? Any that have had no peeling problems. I have OS SF, FX, FXi, and FP engines. Thanks.

I agree.

This is more than simply a lean run... something fouled that engine up badly.

Is the sleeve plated also outside?

Copied from Tower:

"Advanced Bi-Metallic Liner. This process uses a double layer of
plating material rather than one thick layer. This helps the metal
to bond to the cylinder and is more durable. Also, the plating
process is more consistent, resulting in a more precise fit between
piston and sleeve for better compression, longer life."

They use nickel plating in an electrolytic bath and that goes everywere, including the outside. Nickel does not adhere well on its own and one can use chromium as a thin adhesion layer before putting on the nickel, hence the term "advanced bi-layer".

High performance engines only use a thicker chromium layer. This is true for car engines (and some airplane engines) from OS too, but why they insist on making sub-pair airplane engines I have no idea. At least they don't claim to be making ABC engines anymore, like they use to.

I agree though that this engine looks like it has been severely overheated, so more a user error than a fabrication error.

I would send it into towerhobbies and see what they say, there the warentee garentor, they may replace it if it looks faulty,its nice to get opinions from outside the box but you will find there are few consistant answers on any particular subject very one has a opinion and there free to express it,but it doesn't necessaraly meen its fact.

Mr cox believes OS makes sub par engines, not likely since there one of the most reliable glow engines on the market, to each his own.

there has been a few threads on cylinder peeling, if its the case then common sense says that hobby services(towers repair division) would fix or replace the engine as long as there was no obvious abuse to the engine tower backs its products at least it has when I have had any trouble with them in the past

That certainly looks like the dreaded OS peeling problem and it's not uncommon to see the peeling on the outside of the liner too. Unfortunately the only cure is a new piston/liner set but I believe a set from a TT 46 is a drop in replacement and it's true ABC, get confirmation on that first though before you rush out and buy one .

The TT Pro 46 is not true ABC. it is ABN just like the AX but a different process. But it is extremely rare to see a TT Pro 46 peel the liner

I've repaired/rebuilt all sorts of engines including everything from automotive, to industrial, to mowers to RC. Seeing deep scoring and metal transfer on the piston and cylinder wall is a very common sign of serious overheating. Dust ingestion could also cause some vertical scratching but I would expect it to be more uniformly distributed around the cylinder wall. If the engine ingested some sort of larger debris you would likely see some remnants of it and evidence on top of the piston.

Yes, there is some plating damaged on the outside of the liner around the exhaust port. Again, that is likely because that area got extremely hot.

This engine just appears to have been overheated for an extended period of time in my opinion.

Yes, there was a plating issue on certain OS cylinders but that was on specific models from what I understand and it was a while ago. OS makes an outstanding engine and the .46-AX is among their best. No engine, no matter how high quality, can withstand being repeatedly overheated for extended periods though.

It's just an example of learning the hard way. We've all done it in one form or another.

I believe the Magnum XLS-46A liner and piston that is a replacement for the OS 46FX liner and piston, and the Magnum is chrome plated and less expensive. Don't know about the 46AX.

I expect Tower / Hobbico will reject the warrantee claim, but it is worth a try. I had no luck when my 40FX peeled.

What prop are you running and what fuel with nitro and %oil content...maybe that would help....Rog

The sleeve locating pin in the top of the crankcase for the 46AX and 46FX are 90 degrees from each other

I'm not sure what the prop size is, it came with the kit..
I was using 20% nitro.
Umm, I agree it probably ran lean, I never touch that needle valve.

Today, OS agreed to look at the engine, so I sent it to them.

Do you think OS will refund me?

At best they will repair or replace it but no refund