CONFIRMED - It's a Cold-Seizure

[gyropilot]

Well it looks like the cause of the engine failure I experienced in my GyroBee a couple of weekends ago is a case of classic cold-seizure.

I took the cylinders and pistons off and found signs of scuffing between the cylinder walls and pistons. The PTO cylinder, which is the coolest running cylinder on my 503, suffered the worst of it. The mag end cylinder wasn't too bad.

Pictures of the PTO piston (two side views) and the PTO cylinder can be viewed here:

http://home.usaa.net/~gyropilot001/ColdSiezure/Piston1.jpg

http://home.usaa.net/~gyropilot001/ColdSiezure/Piston2.jpg

http://home.usaa.net/~gyropilot001/ColdSiezure/Cylinder.jpg

The damage doesn't look like much, and quite frankly if this engine were in something land-based like a snowmobile or a motorcycle, I'd be tempted to buff out the piston scratches, lightly hone out the cylinders, and put it back together. But since this is an engine which my life depends on, repairs will require reboring the cylinders one-step oversize and fitting new pistons w/rings.

As I've said before, the responsibility for this happening rests squarely on me! I believe I throttled the engine back to idle too quickly (and/or possibly for too long) after being at a full power climb. In the back of my mind I knew that large sudden throttle changes in an air-cooled 2-stroke are a bad thing, but I guess I just didn't understand how bad! Well it's turning out to be a $625 educational experience!

Unfortunately I'm strapped for cash for the next few months due to some previously committed to projects (like putting the finishing touches on a new workshop/garage and getting married), so these repairs are on hold for the time being. I may wait and combine these engine repairs with adding oil injection to the engine and making a couple of airframe modifications. As a result, I'm not sure if I'll even be back in the air this flying season. Bummer! The flying season started off so well and my Bee was performing so well.

No need to rush things though... it's better to take a step back and do things right because they'll always be another day to fly!

Regards,

John L.

[chuter]

Thanks for the update and pics, John. Sorry you'll be grounded for awhile.

[gyroman]

That hurts my wallet just thinking about it. Too bad on missing the flying season. BTW, congrats on getting married. Does she like gyros? What other modifications are your planning for the airframe?

[Chuck Irby]

John, I am sorry that happened to your engine. If you don't mind, would you please give the particulars on the engine, i.e., what oil were you using, how was it mixed, what fuel, how many hours on the engine, and anything else you can think of that might be pertinent?

[PW_Plack]

Uh, John...

My current cynical state of mind forces me to suggest you finish the workshop and the engine rebuild before your wedding day!

Are we still on for El Mirage?

[gyropilot]

BTW, congrats on getting married. Does she like gyros?Thanks.

She's pretty much scared of anything that flies which is smaller than a commercial airliner. Since the Rotordyne project was discontinued a long time ago, I don't think there's much chance we'll see her in a gyro anytime soon. :)

This is fine with me though. She has her interests (facials, shopping, gardening) and I have mine (gyros, metalworking, machinery). This way I don't have to worry about her getting in my workshop and touching my tools!
What other modifications are your planning for the airframe?
In order to add oil injection to the 503, I'll have to move the engine back another inch or so. This will require new longer engine support brackets be made and will in turn throw the static airframe hang angle off so I'll probably need to make new rotor head cheek plates.

Then I'm also getting nervous about that heavy engine (well... heavier than a 447 anyway) being so far back from the mast on those lightweight engine supports, so I'm planning on adding bracing struts from the rear of the engine down to the tail boom.

Nothing too radical.

Regards,

John L.

[gyropilot]

If you don't mind, would you please give the particulars on the engine, i.e., what oil were you using, how was it mixed, what fuel, how many hours on the engine, and anything else you can think of that might be pertinent?
Dual-carb Rotax 503 with dual Ducati ignition.

Texaco Havoline 2-stroke oil premixed 50:1 with regular unleaded gasoline.

Guessing at 150 hours total on engine (I'm the 3rd owner), 25 hours since complete teardown, cleaning, inspection, and reassembly with new gaskets and seals.

I noted very little carbon buildup on the pistons heads and in the combustion chambers, which is probably to be expected after only 25 hours.

The engine seized while at idle just after being at full power. It started to run a slight bit rough, I applied throttle, rpm started to increase, and then it just died as I pushed the throttle to the forward stop. Just prior to the engine seizing all CHT and EGT readings were in the green.

The way to prevent this kind of cold-seizure is to throttle back to a cruise setting for a couple of minutes (to let piston and cylinder temps equalize) before gradually reducing the throttle to idle... like you would normally do in a traffic pattern... and I'd apparently always done before I got a little too careless. Reduce the throttle suddenly like I did and the cylinders cool faster than the pistons.

There's another way a cold-seizure can happen. It's when full power is applied to a not-fully-warmed-up engine after starting. This is common in colder climates in the winter. The end result is pretty much the same as what I experienced, only worse because it happens at full power... severely scuffed pistons and cylinder walls.

Either way you're looking at about $600-700 to fix it. That's $65 per cylinder for boring one-step over, $210 for each piston w/rings, $120 worth of gaskets, plus tax and / or shipping. Painful no matter what.

Regards,

John L.

[ToddP]

Thats really too bad John. I was fortunate that my cylinders were virtually untouched other than some deposits left on them from the pistons. These were easily honed out.

Does it strike you as odd how tempermental these engines are? I just don't think every kid (and adult) riding a 2 stroke motorcycle is taking these kind of precautions to make sure their engines don't seize. Do you think these Rotax Aircraft engines are precision machines with much tighter tolerances than a motorcycle, or just poorly designed with old engineering?

[gyropilot]

Uh, John...

My current cynical state of mind forces me to suggest you finish the workshop and the engine rebuild before your wedding day!
Believe me Paul I was tempted to whip out the ol' credit card and fix the problem right now, but I'm loath to run up a debt on account of this. I just can't afford it.

The first week after this happened I was sick at the prospect of not being able to fly for the next couple of months, but then I started trying to look at the bright side. It can be considered a mixed blessing I guess... I can now concentrate on getting my new workshop finished and maybe also make the modifications I was already planning. The end result will be an even better Bee.

Are we still on for El Mirage?
I'm not sure yet, but it's starting to look doubtful. I'm holding off making a decision just yet. I'll definitely keep you posted well in advance.

Take care,

John L.

[Chuck Irby]

John, thank you for that information. Are you using 87 octain fuel, John?

Did any of you read the independent report on 2 stroke oils on the Ultralight News website? It was pretty interesting. Pensoil looked mighty impressive.

I have started using 4 ounces of Marvel Mystery Oil per 10 gallons of fuel, in addition to the 50 to 1 - 2 stroke oil.

I don't know if you read it or not, but I posted earlier that a friend of a friend on the Mississippi gulf coast has 1100 hours on his 582 without any problems.

[gyropilot]

Does it strike you as odd how tempermental these engines are? I just don't think every kid (and adult) riding a 2 stroke motorcycle is taking these kind of precautions to make sure their engines don't seize. Do you think these Rotax Aircraft engines are precision machines with much tighter tolerances than a motorcycle, or just poorly designed with old engineering?
Todd,

With regard to the cold-seizure issue, I think it's sort of comparing apples and oranges when comparing dirt bikes to our aircraft engines. Do most dirt bikes run at constant high power settings? Are they fan cooled? Not in my limited experience.

Instead, a dirt bike is probably constantly changing rpm and the overall engine temp can't change very rapidly due to the lack of fan cooling. Then, if it does stop running for any reason, it's no big deal to just restart it and continue on.

I don't doubt for a minute that my 503 would have restarted right after the cold-seizure and then seemed to run just fine. I think these engines can take some moderate amount of abuse and still run... at the cost of some reliability. I hear some horror stories of how poorly some 503's are maintained and they seem to be pretty forgiving.

The way it is now with my engine (mildly scuffed pistons and cylinders), it's likely that it'd be more susceptible than before to another cold-seizure if the piston to cylinder wall clearance was reduced for some reason. I certainly don't want less reliability. There are too may trees, wires, houses and water around here!

Regards,

John L.

[gyropilot]

John, thank you for that information. Are you using 87 octain fuel, John?
Yep. I started out using 92 octane years ago until I realized I this was a complete waste of money on not required.
Did any of you read the independent report on 2 stroke oils on the Ultralight News website? It was pretty interesting. Pensoil looked mighty impressive.
Yep... read it years ago.
I don't know if you read it or not, but I posted earlier that a friend of a friend on the Mississippi gulf coast has 1100 hours on his 582 without any problems.
I have an UL trike friend in Oregon who said he has in excess of 800 hours on his 503 without replacing the crankshaft. A fixed wing UL pilot friend of his had a 503 crank fail at 150 hours, which stranded him on an Oregon beach overnight.

**** happens!

John L.

[Ralph]

John,

Sorry to hear about your engine! You didn't mention it one way or the other, but was there any ethanol in the fuel you were using?

My main question concerns your decision to go to oil injection. While more convenient then pre-mix, you have the added hardware that, if it fails, can trash the engine. Premix isn't cool, but if the oil is in the gas, you get the oil as long as the system is moving fuel.

Ralph

[GyroRon]

No way I could be out the rest of the summer. I would hone the cylinders - lightly! - and put in new pistons and rings Standard size and new gaskets of course and get flying. One days worth of work max.

You mentioned running 87 octane gas. Tell me more.... I thought it was bad to run less than 92 in the Rotax two strokes. I myself use the cheapest 87 octane I can find in everything I got that runs on gas including the gyro, Phantom and Piper - I have a autogas STC for it -

[gcrisler]

John

Most likely the cylinders are not scored up, just aluminum deposits on top of the cast iron. I work at a engine shop for 10 years, you can go to the hardware store and get some muratic acid ( HCl) and wipe the acid on the aluminum. This acid eats the aluminum quickly and leaves the cast iron virtually unaffected. Leave the acid on for about a 1/2 hr. and wash it off with water, repeat this until the aluminum is gone. Next hone the cylinder and then wash it out with liquid clothes detergent soap and water, this is important as it removes the hone grit. Brake cleaner or WD40 doesn't do the trick only soap and water.

As far as the few gaskets you need do a google search for "online skidoo parts" you will find many sites that now have online parts breakdowns, pick a sled from 1990 that has the 503 engine and order what you need. Here is a site I found in about 1 minute

http://216.37.204.202/Skidoo_OEM/Skidoo.asp?Type=13&A=60&B=4

Most of the 503 parts have the same part numbers as listed in the CPS catelouge.

I also run the cheap car gas, 87 octane, and have about 20 hours in a 503, 30 hours in a 532 and 32 hours in a 582. I have never had a low octane fuel related problem.

I also had a Skidoo 583 engine in a sled I had for 3 years, I ran this on low octane fuel and never had a problem. The sled pumped out about 90 hp and the 582 aircraft application developes only 65 hp.

Garret Crisler

[gyropilot]

You didn't mention it one way or the other, but was there any ethanol in the fuel you were using?
Based on previous testing, the county where purchased, and the time of year purchased, I don't believe so Ralph. However, I did not specifically test the batch of fuel I was using. I still have about 4 gallons of it, so I'll go back and check that out.

Do you have some reason to believe the presence of alcohol in the fuel would make the engine more susceptible to a scenario like this? If yes, how?

My main question concerns your decision to go to oil injection. While more convenient then pre-mix, you have the added hardware that, if it fails, can trash the engine. Premix isn't cool, but if the oil is in the gas, you get the oil as long as the system is moving fuel.
I understand your concerns Ralph, but will all of the cross-country flying I like to do, premixing is a major PITA. I'm going to oil injection as a way of avoiding carrying bottles of oil in my flight suit pockets and then having to deal with the blending hassles when refueling at airports.

Best regards,

John L.

[gyropilot]

No way I could be out the rest of the summer. I would hone the cylinders - lightly! - and put in new pistons and rings Standard size and new gaskets of course and get flying. One days worth of work max.
Ron,

This past winter when I took my 503 apart for decarboning and inspection, the my mag end cylinder was right at the maximum out-of-round limit (0.0001 over actually), so I was planning on boring the cylinders oversize after a couple of flying seasons anyway.

Besides, when you're bleeding money to replace the pistons, rings, and gaskets anyway, what's another $130 to bore the cylinders? :)
You mentioned running 87 octane gas. Tell me more.... I thought it was bad to run less than 92 in the Rotax two strokes.
The Rotax 503 manual doesn't specify a conventional "(R+M)/2" octane index rating we're used to seeing at the local gas station here in the USA. The (R+M)/2 is the formula to derive the average of the "Research Octane Number" and the "Motor Octane Number."

The Rotax manual does specify a minimum of 90 RON though. The RON is commonly used in Europe at gas stations.

The RON is typically higher than the MON. Thus, the typical 87 "(R+M)/2" octane index we see displayed on a USA gas pump is about the equivalent of a 90 RON fuel as specified in the Rotax manual.

In short, Rotax specifies *regular* unleaded, ethanol-free gasoline be used in our 2-stroke engines. If pinging is a problem, we're supposed to use a higher octane fuel. Simple as that.

Regards,

John L.

[gyropilot]

As far as the few gaskets you need do a google search for "online skidoo parts" you will find many sites that now have online parts breakdowns...
Thanks for the lead Garret.

Regards,

John L.

[Udi]

I have started using 4 ounces of Marvel Mystery Oil per 10 gallons of fuel, in addition to the 50 to 1 - 2 stroke oil.

I've talked with an airboat company who is using Rotax 618 in their boats. Their mechanic, a guy by the name of Beaver, told me he is adding MMO to the fuel once in a while. He said the engines run for well over 1000 hours without major maintenance needed.

I don't think the MMO can improve the life of the crankshaft, but I guess it helps removing carbon and other deposits. Some people add it to the 100LL to remove led deposits. The longer engine life must have something to do with the way the engine is being used.

You are not supposed to use MMO for the first time in engines that already have large accumulation of deposits. Loosening large deposit may damage the engine.

Where do you buy the MMO, Chuck?

Udi

[RHerron]

Garret,

Thanks for the excellent info!

[GyroRon]

You can buy MMO at most any autoparts store. It isn't very expensive either. I use it in my Pacer, a few onces every other fill up. Haven't used it yet in the gyro, but did put some in the Phantom once or twice.