Rotax 2 Strokes - Durability

[Chuck Irby]

It might be helpful to many of us if those of you who have had to rebuild a Rotax 2 Stroke would list the circumstances:

1. What was the engine model?
2. How many hours did the engine have on it when you decided to rebuild it?
3. What caused you to have to rebuild it?
4. What oil did you use in it?
5. The condition if the main parts, i.e., how badly worn were the rings, the pistons, the cylinders, the rod journals, the main journals, etc.?

Anything else that you think might be of interest to Rotax owners

[Udi]

I would also like to know if anyone using a Rotax 2-stroke engine ever had a crank shaft failure and, if you did, in how many hours.

Udi

[Chuck Irby]

Thanks for your input Udi. If we can get some participation on this thread, we should be able to come up with a wealth of information.

[gyropilot]

It might be helpful to many of us if those of you who have had to rebuild a Rotax 2 Stroke would list the circumstances:

1. What was the engine model?
1994 Rotax 503DCDI
2. How many hours did the engine have on it when you decided to rebuild it?
Once at about 75 hours and again at about 150 hours.
3. What caused you to have to rebuild it?
I bought the engine used with *supposedly* 25 hours on it. Based on other circumstantial evidence (3 previous owners, used on a gyro flown by 2 of them), I suspected it had at least 50+ hours on it.

When I estimated this used engine had between 75-100 hours on it, I decided it was time for a teardown, cleaning (decarbon) and measuring of internal parts against wear limits just to be safe. A complete Rotax gasket and seal set is less than $130.00, and if no machining is required, the complete rebuild only takes a weekend to do. I found nothing unusual in the process... peace of mind.

This past winter, during the non-flying season, I decided to do another complete tear-down, cleaning and measuring of wear. I've found the parts wearing as normal, mainly the cylinders were slightly larger, but still well under the maximum. I did discover the front cylinder is right at the maximum out-of-round limit, but I decided to let that go until the next rebuild cycle when expensive cylinder reboring (or replacement) and new pistons will be required.

Based on the cylinder wear, I'm even more convinced the engine has between 200 and 300 hours or more.
4. What oil did you use in it?
I've used AV-2 and now use Texaco Havoline.
5. The condition if the main parts, i.e., how badly worn were the rings, the pistons, the cylinders, the rod journals, the main journals, etc.?
As previously mentioned, everything was well under wear limits with the exception of the front cylinder out-of-round. Carbon buildup on the top of the pistons and inside combustion chambers was minimal and removed.

The only thing of note was carbon buildup up under the piston dome (above the wrist pin). Apparently the underside of the piston gets very hot and the fuel/oil mix exposed to this surface burns to a thick glass-hard film up under there. I had to scrape that off during both rebuilds.
Anything else that you think might be of interest to Rotax owners.
The Rotax 503 is probably the most forgiving, simple to use, easy to maintain, bullet proof, air-cooled 2-stroke engine available for light aircraft use. Mine has never given me the least bit of trouble and has always run perfectly.

2-stroke engines do require more periodic maintenance than 4-stroke engines, but they make up for that by being so lightweight, relatively inexpensive to buy, easy to maintain, and inexpensive to rebuild.

If 50HP is adequate for an application, I highly recommend the Rotax 503. As long as the published maintenance schedule is followed to the letter, you will rarely ever hear of a failure.

Regards,

John L.

PS: I have all of the engine measurements documented and can share them in case anyone ever needs them to compare to their particular Rotax 503.

[Doug Riley]

I rebuilt the 1985 447 on my old Air Command at about 180 hours. It was getting gnarly to start. Upon investigation, I found that the rings were jammed in their grooves, no doubt leading to loss of compression --at least until she got warmed up. (The problem was worst in the winter.)

At the time, I followed the G.A. practice of filling the tank before I put the gyro away for the day. As a result, I was burning tanks of 100% stale gas.

I didn't know about Rotax's recommendation of 150-hour teardowns. It wasn't mentioned in the primitive manual that came with the engine. I used AV-2 -- not necessarily the very cleanest-burning of oils. I also didn't fully appreciate the degree to which auto gas turns to varnish when it sits for weeks in a tank or can.

The rings were so stuck that I ended up ripping them out in pieces with Vise-Grips. After cleaning the grooves, I paid the $100 for a new set of rings, installed them and ran the break-in sequence again.

Having learned a lesson, I drain out stale fuel and burn it in my lawnmower, and also check the rings' freedom more frequently. With luck, you can catch the buildups in time to free the rings before they are hopelessly stuck.

[mceagle]

I have had the dubious privledge of servicing and repairing many Rotax two strokes in my area, including several of my own. First problems ranged from seizure during run-in to piston replacement at 1300 hrs.
I could write a book on this but I will try to keep it as brief as possible. Every time you have an "unscheduled" termination of engine noise resulting in a forced landing, you loose a little more confidence and gain a few more grey hairs. And each time you have another engine flame out, it takes a little more time before you are once again confident enough to fly over country that you cannot land on. In the end, you stick to clear country and are constantly surveying your landing options.
This is not conducive to enjoyable flying.

I will try to list as many of the failures as I can remember.

8 broken crankshafts on 503, 532 and 582. All broken in the centre between the two cylinders. It happened with both standard cranks and the later model beefed up cranks. Times varied but mostly between 300 and 400 hours. This seemed most common on engines regularly run at the high end of the cruise range.

6 failures of conrod big end bearings on 532 and 582. (Usually resulting in the conrod fracturing the bottom of the crankcase).

Many failed engine bearings on gearbox end of crankshaft (503 and 532 with "B"gearbox).

1 crankshaft centre bearing failure at 30 hrs, causing damage to "compression" seal and total engine failure (532).

X plus Holes blown in pistons. (all engines)

Many cracked pistons (Mostly 532) causing seizure.

Many low hour partial "clearance" seizures of early model 582's

Failure of waterpump seals on 532 and 582 models, some over time and some instant.

Partial Ignition failures on points engines due to faulty condenser. (Failure did not cause total failure but intermittent missing).

Several failures of one of the CDI ignitions on a 582. (does not cause engine failure)

Sticking needle and seats resulting in over rick mixture, caused by wear in float pins. (all models)

Intermittent missing caused by vibrating "spade" connection on ignition coil (mostly on 503)

Over rich mixture caused by wear to both needle jets and jet needles.

Lean mixture failure caused by failure of the carburettor needle retaining clip (vibration)

I had better get back to work - I will add more as they come to mind.

[Aussie_Paul]

Tim, now I know why you go for the Soobs and the 4 stroke Rotaxes for the working machines!!!!!!!!!!

Aussie Paul.

[automan1223]

2 strokes are paticuliar about many things. when I bought a supposdly super low time rarely used 503 from a clown in texas I reached around and grabbed my ankles. I knew I was taken when the engine arrived with a red tag on the rotted wooden bananna crate from ups with parts jingling around like it was used in a foot hockey game.

This engine would not start when I got it on my machine. So much for low time rarely used. The compression was sooooo low it was pathetic. 40 in the front, 60 in the rear cylinder. I way over paid for a used dinosaur engine. When I do things I do them RIGHT ! I do this for a living but rotax parts are mighty expensive. Even with free labor. I spent over 1500.00 to make this engine right. The compression was up around 140 after I was done with it.

I ended up with 2 new pistons, wrist pins, wp bearings, rings.

the cylinders had been replaced some time in the past and were in the middle of the spec but the dummies put the old worn pistons and rings on them. I honed the cylinders to clean them up. For the new rings.

The mag and pto bearings were actually tighter and in better shape than the new oem rotax bearings that I installed. I had to update the dino carb as there were many improvements to it in the past. I put way to much money into the engine for what it was and it stung even more when it was under powered for my craft. Power to weight.

When I finally sold it had 10 hours tops on it and was broken in nicely. Started on the first pull. If the crank and cylinders were not in good shape I would have wasted 600 bucks on a boat anchor. Buyers Beware of used equipment unless you KNOW the seller. AND KNOW THE TRUE HISTORY OF THE Parts/engine. If not dont pay them more than scrap for your parts.

I ran the 2 oil mix from CPS, its a good oil and well suited for 2 strokes.

ANY engine that is neglected in ANY way can fail at any time after what we demand from it. That includes bad gas. And NO 4 strokes are not more tollerant of abuse they only turn at lower rpms so they get away with the neglect longer.

I almost got shafted again from another yo yo in Pennslvania. He left an engine 2.5 for the last year at least with a rag stuck in the intake OUTSIDE. The engine would not turn over by hand. Tear down revealed the best. No rust, just dried out carbon stuck in the quench area fell to the bottom of the cylinders and held up the rotation. I brushed it out and everything was ok. However I did not pay this guy until I knew the engine was good.

Proper engine inspection / rebuild / maint / is everything in an engine used on an aircraft !


Jonathan

[mrford61]

1990 model single ignition 503 with "B" box.

At 192 hours an in flight seizure (attention grabbing). Strip down revealed melted piston. Definately my lack of understanding of 2 stroke maintenance.

After a $1800 complete rebuild by a Rotax dealer it flew only 4 hours before bogging down to about 2000r.p.m. causing another unscheduled pit stop. This one was spectacular with a trail of smoke following me down.
The rear engine seal was not the right one, crankcase compression popped it out of its place and the crank took in gearbox oil. yeeehaa!!

Nothing in the world beats good training.

[Chuck Irby]

John Landry, Doug Riley, Tim McClure, Jonathan Weis, Mark Clifford, excellent reports. I really appreciate you sharing your experiences with the Rotax as you have. Between us all, we have a wealth of experience with the Rotax engines.

Anything more that you, or anyone else, can add to this thread would be most appreciated. Rebuilding a Rotax ain't cheap. So the longer we can get them to perform for us, the better.

When I initiated this thread, I was hoping to learn that there was a "miracle oil" that could be used that would make the typical Rotax 2 stroke last 2,000 hours (you know I'm not totally serious). However, we all know that there are certain things we can do that will prolong the life of any engine, 2 stroke or 4 stroke.

When I crashed a couple of months ago, I was forced to remove the head from my 618, due to having to weld up a hole in the outer wall of the rear cylinder. There were no carbon deposits anywhere. The top of the cylinders, the tops of the pistons and the combustion chambers in the head, were all clean. I have been using a synthetic oil and my engine has 75 hours on it.

This is significant: My son Chip's instructor, told him about a guy who has around 1100 hours on a 582, and has never had to overhaul it. He has performed many inspections but never found any significant problems. He supposedly uses the cheapest oil he can find, Walmart's brand was mentioned, but he does use an ounce or so of Marvel Mystery Oil per 5 gallons of gas. I have been a believer in MMO for many years. I will try to get more info on this and report it.

[mceagle]

Another one I forget to mention was the regular failure of the caged needle bearings on the early 532's. In the worst case scenario, a broken piece of needle bearing would find its way into the rotary valve and render the crankcase unservicable. Any engines purchased or serviced after a specific date should have had the caged needles replaced with the later cageless type.

Something worth mentioning is that the failures did not seem to have any relation to what type of oil was being used.

Those engines that did give long and dependable service were, without exception, engines that were run nearly exclusively on low throttle settings.

[Chuck Irby]

Tim Mc, I would venture that you have more experience with the Rotax 2 stroke than probably 99% of us. I have a lot of experience with 2 stroke outboards, but virtually none with the Rotax.

I normally climb out between 6000 and 6650 engine R's, but do a lot of my cruising between 5200 and 5400. Would you consider my cruise RPM to be "low throttle settings"?

[barnstorm2]

Tim,

I have not seen much mention of the 447. It sounds like mostly the 5XX series.

[Aussie_Paul]

I ran a 582 with a "B" box for Bert Flood, the Oz Rotax dealer. Rotax had suplied a 582 to Bert that needed to be run quite hard, and Bert asked me if I was interested in running the engine and documenting the operating conditions, temps, etc. while I was training. I was, at that time, using a side by side Air Command with the super thruster kit (68" prop & raised engine) with 27' Skywheel rotors.

I said that I would love to be part of a program like that. No one was allowed to conduct any maintainence on this engine at all. I had to use the Super fuel that was availible in OZ at that time, this was in approx. 1993. The first 40 hours were to be run using one of the Vavoline oils. In the single ignition 532 I had a lot of plug fouls with this particular Valvoline oil, BUT said that with dual ignition I would go with their requirements. I had to document the egt's, water temp, OAT, QNH etc for each flight.

After the 40 hours I was to run the Castrol mineral oil Super TT, with the Super fuel. I could not believe the carbon build up on the plugs with the Valvoline oil!!!! Obviously with the dual ignition when a plug fouled the other plug kept working until the carbon was blown off the second plug. This engine had some mods done to it and Rotax wanted it back after 400 hours. The agent did not know what the mods where. Other than having a bearing in the "B" box fail, I flew this engine for 560 hours before it was sent back to the Rotax factory.

The only difference that I could detect, as an operator of this engine, was the water temp was 55 degrees C instead of the normal 80 degrees C. They must have fitted a 55 c degree thermostat instead the usual 80 c. I never had one ounce of trouble with it, and at one time it started 18 times in a row first pull. This was 9 cold starts and 9 warm starts.

I conducted 1560 hours in my Air command and never had to forced land due to a Rotax engine failure. I used a 532 for approx 220 hours, and then changed to a dual ignition 582 that domed the 2 pistons at 360 hours and was a wreck at approx 500 hours, the 560 hours in the test engine and approx 260 in the 618 that I finished with in the machine as I went to the Raf machines. The 618 was very nice. A 4% increase in gross weight and a 15% increase in HP.

I much prefere 4 strokes for 4 reasons.

1) they idle at a rpm that does not have the machine moving off on its own.

2) the reduced vibration levels in flight.

3) the more efiicient use of fuel.

4) the average person can operate a 4 stroke without having to be "like a
mother watching over her baby" as you do with 2 strokes.

I loved the power to weight ratio of the 2 strokes back in 1987. That is all we had to get 2 people flying for training purposes, and they served us well at that time.

These days, with my training and more cross country work, I just love using 4 strokes.

Attached is a pic of the modified A/C that I used between 1987 and 1997. The pic was scanned in 2000.

Aussie Paul.

[PW_Plack]

Gyropilot (John Landry) said:

"If 50HP is adequate for an application, I highly recommend the Rotax 503. As long as the published maintenance schedule is followed to the letter, you will rarely ever hear of a failure."

Well, you'll hear of one more when John gets back to his computer! I just got off the phone with John, and had intended to drive up to watch him fly in the warbirds airshow at Olympia, WA. He won't be flying today, because yesterday, he had an engine failure.

The bad news: Thousands of people were watching.

The good news: John's fine, made a routine no-roll landing on the runway, and best of all...the PA system failed just before John's engine did, so maybe the spectators will think it's all part of the act.

I'll be anxious to hear the details, because nobody's more careful with maintenance than John.

[barnstorm2]

Paul, Thanks for the news!

John, Glad to hear you are alright and got to land on the runway. Once again good skills, training and the safety of our little birds in an engine out saves the day.

Making a guess on no info here but I'll second Paul statement that the spectators probably thought it was part of the act, and I'll also bet more than half did not realize his engine went out!

[scott heger]

Paul, great overall view on Rotax's. I have a 582 on my SportCopter. It has been good to me so far. I have had two "non scheduled" landings with it. The first one I had a Muikini fuel pump failure after two years of use. I had just filled the gyro up with fuel at the airport and was taking off. As I started climbing out I felt a small hesitation. I decided to climb more vertically than forward than normal over the runway. This ended up being a good decision, because 15-20 seconds later, the engine quit without any further warning. I was able to excute a quick (and low) 360, and land within the last few feet of the end of the runway. Nothing like running out of fuel with a full tank.The fuel pump had given up, and have since been advised to change them on a yearly basis. However nothing is mentioned as this being a regular maintance item in the rotax owners manual. This was not a engine failure, per se, but the fuel pump was the original supplied with the engine.

The second time the engine had 150 hours on it. when I took off I noticed a lower power situation. The tach was reading 300-400 RPMs low and climb was very lazy. I did not realize the problem right away and had cleared the end of the runway and was over trees. I turned back towards the airport into a 15mph downwind, and began a immediate sink. The sink was slow enough that I was going to make it back to the airport , but not all the way to the runway. I landed on a grass area of the airport without further problem. The engine was checked and had poor compression in the rear cylinder. A top engine teardown revealed a stuck lower ring on the rear piston. I had been experiencing the rear carb bowl(with sits lower on a SportCopter), filling with oil upon sitting over a week from the oil injection pump leaking down. I normally emptied any oil before flight , but not always. Sometimes I would just let it burn off while warming up. I believe this extra oil caused the ring to stick. I cleaned the rings, and all internal measurments were still good. After putting it back together, the oil pump has stopped any more oil leakdown (mystery cure). The engine is now running better than ever at 200 hours.

The bottom line is I had a little luck riding with me in both instances , as well as I spend time every flight practicing a emergency procedure or two. I was completely prepared and had thought out what I needed to do in the situation that I was placed in, which resulted in no damage to the gyro or me. Things happen very quickly when the motor goes quiet, and all you hear are the blades spinning, and wind. Living in Southern California presents a special set of circumstances that most 2 stroke flyers don't have to worry about. Basically I fly a large percentage of my time flying over highly populated areas. I try to fly along routes that present emergency landing spots. It may be a river bottom , or the flat roof in a industrial building. Hey at least all those Wal-marts popping up are good for something. I routinely practice landing on a helipad, instead of the runway, and have become pretty good at spot landings. Practice is the key to successful emergency landings.

Scott Heger, Laguna Niguel, Ca SportCopter N86SH

[mceagle]

Chuck I,

The "Drifters" that are regularly run at 5200 to 5400 are the ones that clocked the best hours, usually over a thousand hours with 503's. Mostly too as soon as they are safely airborne, they throttle back to approx 5800 for climb.
If I remember rightly, Rotax released a bulletin saying that the critical "harmonic" vibration range was 5800 to 6100. This was unfortunatly the range that I wanted to operate my two seater in.

[craigjackson]

Scott,

I, too, have experience the same phenomenon with the rear carb bowl filling with oil on my Vortex. Generally, if I haven't flown in over a week, I usually remove the bowl and empty the contents before starting the engine. Any clue as to what you might have done to eliminate this?

[Dean_Dolph]

Scott, now that you have related your experiences, don't you think it is time to change your signature block to read 'You're only as good as your last landing'?! :D

[scott heger]

Dean, I consider "the last flight" to include the landing also.

Craig, I did mess with the adjustment to the oil injection pump some. It was slightly rich(open) from the two alignment marks. I moved it a little bit to align exactly and this seemed to solve the problem. I always believe a little too much oil is better than too little....but...maybe not in this case. According to Jim at SportCopter, this seems to be a hit and miss problem, depending on the oil pump. The problem went away for me at least. I just flew after being away for 3 weeks on thursday, and not a bit of oil in the rear carb bowl. Engine started on the second pull, and i flew over 100 miles to san diego county and back that day in nice and clear 82 degree weather.


Scott Heger, Laguna Niguel, Ca SportCopter N86SH

[Chuck Irby]

Tim Mc, thank you for your reply about the rpm ranges. This is good to know. Being a drifter is my favorite kind of flying, but I didn't know it had a name.

Tim, was there a noticeable difference between the air cooled and the liquid cooled engines?

Has anyone had experience with Marvel Mystery Oil? I have a friend who has been putting it in his automobiles, both the crank case and the fuel tank, for years. He swears by it.

[scott heger]

Tim and Chuck, I believe the RPM range you referred to might pertain to the "B" gearbox, more tahn the "C" gearbox. A mechanic told me that the "B" transfers alot more harmonics/vibration than the "C" to the crankshaft.

Scott Heger, Laguna Niguel, Ca SportCopter N86SH

[Chuck Irby]

Scott, I have heard similar things about the "B" box.

One other thing I've heard is that the engine and gear box will hold up better with the use of a clutch. I did install a clutch in my "C" box a while back.

[barnstorm2]

Doug,

Did you notice a loss of power on your 447 before you did the rebuild?

Any issues with the A box?

[Doug Riley]

Tim: The 447 never HAD any power to begin with...

Seriously, no, once it got lit, it ran just fine. I noticed no difference in the power output as the engine aged. The startup performance got steadily worse over about 3 years, however. Sometimes my hand was blistered and bleeding from yanking on that rope before she would go.

Yes, the A box -- specifically the lack of sufficient Belleville washers in the slip joint -- was part of the problem. The engine would kick over, sputter, clatter and smoke for a few revs and then stop. I believe this was partly the fault of the slip joint bottoming out too easily as a result of insufficient washer tension (well, compared to the mass of a 3-blade prop at least). I haven't run into these symptoms in newer Rotaxes with the larger washer count.

The old choke (enrichener) system didn't help the starting situation, either. Neither did mounting the engine upside down, so that fuel and oil flooded the sparkplug cavity if it didn't start right away.

[cgmg]

I'm flying a 503 with Bosch ignition, dual carbs, unknown year of build. Bought from a friend who thought he had about 125 hours on it. Using a "B" box. Two years ago, tore it down, put new rings, 3 new O-rings, both end seals, and new gaskets in. It had a little bit of carbon buildup, one ring on each piston had one small area that was stuck. Cylinder walls looked good, and we cross-hatched cylinder walls.

Next year, my wife flapped our McCutchens, and blew our Powerin prop. One month later, while flying my friend's Dragon Wings, I slightly dented them as I flapped the Dragon Wings.

This year, with about 325-350 estimated hours on the engine, I started seeing a light quantity of fuel and oil dripping out of the #1 cylinder air filter when I landed. In one week this summer, had two engine cowling bolts come loose, and go through the prop. The last one was while my wife was flying, and it made the prop unflyable. Also, when she landed, fuel and oil were dripping off the air filter.

Needless to say, the engine is in the shop being rebuilt. The repair guy tells me there was little or no carbon buildup on the pistons, with the exception of under the piston dome(large deposits there). All rings were free, need very little cleaning. There were some minor carbon scratches on the cylinder walls, below the exhaust ports. Not enough to require honing. Some indication of piston slap, as I ran for a couple of weeks with RPM's of 6700 or so until I re-pitched the prop. The big issue was .005" runout on both the mag and pto end of the crank. Most likely due to the two prop strikes. One of the bearings sounds growly, so replacement was recommended. The repair guy is leaving the decision on the other bearing to the crank repair guy. No word on that yet.

Even the day my wife flew it last, it would start on the first or second pull, if primed. I'm having CDI ignition installed, along with ceramic head pistons, which should cure the carbon deposits under the domes. The repair guy said it looks like I have the jetting down correctly, based on the lack of carbon, and the way the plugs looked, with about 20 hours of use on them. I had been using Pennzoil until recently, which I switched to Havoline after reading all the comments regarding good results with the Havoline. Looks like now I may not have needed to, based on the lack of carbon deposits. I'm glad I still haven't sold all my old Pennzoil, which I have a lot of.

Prior to this, the only problem I had was at about 50 hours of my piloting time, one of the coil wires was worn through by the flywheel(my friend's fault), and I had an unplanned landing in a bean field. But thanks to my instructor's training, and lots of engine out practice, it was a non-event. The only downfall was a lost day of flying at the fly-in.

The only thing I'm unhappy about is that two weeks after I sent my engine in to be rebuilt, I read in my latest ASC magazine that Rotax has the trade-in deal for $2500 now. Two weeks earlier, and I would have been the proud owner of a new Rotax.

I really like the simplicity of the 503, but there are days when it would be nice to have a little more oomph in the engine. Fortunately for us, both my wife and I are lightweights, so the 503 is adequate for us right now.

Hope this adds to the knowledge base for everyone with their 2-strokes.

[Chuck Irby]

Great report Mark. Thanks a lot for taking the time to share it with us. I hope you're back in the air real soon.

Mark, what fuel have you been burning in it?

[cgmg]

Chuck,

I burn regular, non-ethanol blend. I buy from either of two Casey's near me, so I can trust the fuel to truly be non-ethanol. My gyro flying buddy has been using cheap grade gas for the last 8 years, and has never had a fuel-related problem with his engines. He figures he has 700-800 hours of flying time so far.

[GyroRon]

I use 99 percent of the time, the cheapest 87 octane unleaded I can find. I use it in everything from my Pacer to my Rotax stuff, lawn equipment, trucks etc... Never had a problem

[Aussie_Paul]

Hey Ron, you sell everything before they have time to give trouble!!!!!!!!!!! :)

Aussie Paul. :)

[Chuck Irby]

Thanks a lot Mark, and you too Sir Ron of the C's.

[GyroRon]

Aussie Paul, just sold another last night. My Phantom ultralight is no longer mine. Gonna miss it!

[joeheli]

Chuck I know Which oil you are tacking about " Blue Marble oil". Rick "go,go Gadget owner " Recommend that for the mac engine. I got a gallon of Blue marble at home, is expensive!, but I believe is worth it. I still haven't use it until I finish my machine, but Rick use it on his Super Mac 90 and what he tell me is impressive about what does do with the mac's I think that is why allot of people don't have no more problems whit there Mac engines. There's some people that sell it on ebay. Just write "blue marble oil" and you will find it. Or ,I just copy and paste a link of some reviews. I hope this cod help:http://www.maximumsled.com/products/reviews/SterlingTech/bluemarble_review.htm

[Chuck Irby]

Jose, "Marvel Mystery Oil" is the name of the product I was talking about. It is used in addition to whatever 2 stroke oil you want to use. You can buy it at Wal-Mart. Just use 2 ounces per 5 gallons of fuel, in addition to the 50 to 1 two stroke oil.

[joeheli]

Oh! I think I found some info of that mystery oil, I just copy and paste from a link:

"MARVEL MYSTERY OIL
Marvel & other solutions to the lead problem
For all practical purposes, 80 octane aviation gasoline is no longer available, forcing the Cub driver to choose between 100LL avgas and 87 octane automotive gasoline (assuming that he has the necessary STC and that "mogas" is sold at the airport). Each fuel has its own problem. Despite the low-lead designation, 100LL contains too much lead for the older, low-compression engines. Mogas, on the other hand, doesn't have enough: some lead is needed to lubricate the valves.
Robert Parker uses Marvel Mystery Oil to reduce the buildup of lead from 100LL. He explained why in a post on the Cub Builders mailing list, which I have adapted here with his permission. Bob's article is followed by an email I received from Terry Lutz, expanding on Marvel and the alternative TCP. -- Dan Ford

That Marvel-ous Mystery Oil
by Robert Parker

Back in the late 1940s and early 1950s, at military air bases there were 55-gallon barrels labeled MMO (Marvel Mystery Oil). I forget the MIL spec number.... We had charts that told us how many gallons of MMO to put in per tank of fuel.

72 octane is the highest grade of gasoline that can be manufactured without [additives].

80/87 has 0.50 ml TEL [tetra-ethyl lead] per gallon and is dyed RED

91/96 2.00 ml TEL per gallon BLUE

100LL 2.00 ml TEL per gallon BLUE

100/130 3.00 ml TEL per gallon GREEN

115/145 4.60 ml TEL per gallon PURPLE

The amount of TEL in the higher grade fuels has increased the lead build up and fouling of spark plugs, along with valve erosion incidents, reported on some lower compression engines.

You know when you pull a magneto check at the runup area after a considerable taxi to get there, and you are running straight 100LL. You have a RPM drop that is excessive, and run the engine up to a higher RPM for a few seconds and then recheck gives a normal drop.

Why does this happen? There is a bromide chemical in 100LL that is supposed to keep the TEL vaporized and the excess pushed out the exhaust, and this bromide has to be at a certain temperature to work correctly. This temperature can only be achieved in our small engines at 1100 to 1200 RPM. How many of us taxi at this RPM? (If you answered, I do, how often do you have to change your brake pads?)

The automotive gasoline option. There there are two STCs on the market for mo-gas, EAA and Petersen. (I use Petersen's. If you have a question and call, Petersen has an answer for you. EAA has an answer, after 5 different people and the fifth one says let me check and I will get back with you. Sometime they do, and other times that's the last you hear.) Petersen's STC allows for mixing of av-gas and mo-gas. You can put mo-gas in the tank 75% (TEL 0.002 ml) and 25% av-gas (100LL at 2.00 ml TEL) and you have the same 0.50 ml TEL that 80/87 had.

Another way is to run about three tanks of mo-gas and the fourth is a tank of av-gas (100LL) Either of these work OK. That fourth tank however, you will still have the spark plug fouling syndrome.

The TCP/Marvel Mystery Oil option: These are most likely about the same thing, with small changes in the recipe, so as not to infringe on another's copyright. Both are high in detergents to do the cleaning job. Neither should be used for the first time on a high time engine; about half TBO or less should be the cut-off time, for first use.


IN OIL SYSTEM
Use one pint Marvel Mystery Oil about 5 hours before oil change. If screen type system, be sure to clean screen. Then, in the new oil, install one-half pint MMO. This cleans the carbon and sludge collected in the engine passages and crevices and hydraulic lifters, and stores it in the bottom of the oil kidney. Some will make it to the screen, but either place it will be removed at oil change.


IN THE FUEL SYSTEM
Use the directions on the back for amount to put in the fuel per gallon of fuel (4 to 6 oz. per 10 gallons of fuel). MMO goes through the carburetor as a droplet, broken up like the fuel. When it enters the combustion chamber and the gasoline ignites, it is vaporized and soaks into the carbon buildup on cumbustion chamber walls, valve guides, around the valve stem, and on the spark plug. It soaks into the carbon and eventually loosens it up and it goes out the exhaust system.

Now you know how it works, I will neither recommend or not recommend the procedure. Like Fox News says,"I report and you decide". I do know it will help when lifters start to be lazy and not do their job. When valves are beginning to stick, it will free then up. Some people swear by it, some people swear at it, but results is what really tells the tale.

Marvel Mystery Oil and TCP
by Terry Lutz

Since 80-octane fuel has disappeared from Michigan, there has been a lot of talk about what to do so that lead fouling can be avoided in the smaller and older engines. The leading theory is to use Marvel Mystery Oil. This is generally regarded as good stuff, and a lot of people are using it. Mystery Oil is a top cylinder lubricant, so when it vaporizes during combustion, oil droplets are spread around the valves, guides, and rings to keep things moving. It works, and has for a long time. The old timers would use it to free up stuck rings and valves by giving the engine a "Mystery Oil Enema". The trick on a 65 hp Continental is to take the primer line off the carburetor, hook up a tube, and run Mystery Oil through directly through the carburetor while the engine is running. This creates great clouds of smoke, and extends engine a life for a few more hours. You can also just pour the stuff into the cylinders and run the engine.

Then there is ALCOR TCP. This is a fuel additive specifically designed to scavenge the lead from the fuel to keep lead from ever forming on vital engine parts. But how does it work? Inquiring minds want to know, so I called the 800 number on the side of the can. A nice fellow named Rick told me that TCP stands for Tri-Cresyl-Phosphate. It was created during WWII because the cooler cylinders on the multi-row radial engines would lead foul, creating lots of engine problems. Remember too, that lead is added to aviation fuel to boost octane rating, and with the high manifold pressures the wartime engines were operating at, Tetra Ethyl Lead (TEL) was a necessity.

When piston engines passed by the wayside in the military, Shell Oil bought the formula for TCP and used it for years in car gas, which was also blended with TEL. Of course, when unleaded fuel came out, there was no further need for TCP. But aviation fuel continued to contain lead, so the formula was purchased by ALCOR. 100LL fuel still contains 4 times the lead that our friendly 80 octane had. So, "How do it woik?" At the instant of combustion, there is a chemical reaction between TCP and the lead in the fuel to form lead phosphate, which comes out of the exhaust stack as a grey powder. The lead does not remain in the engine, and can't build up on valves and guides to mess up your engine. It only takes a few ounces of TCP to treat 10 gallons of gas. However, the carrier is toluene, and there's some xylene in there, too. You don't spill this stuff on your paint job, and is difficult to carry it with you in the airplane. The container says not to do it. Be careful and informed out there!!"

[joeheli]

Chuck and they are selling some on ebay 32 FL OZ. CAN :
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=35682&item=3690036098&rd=1

[Chuck Irby]

That's good information, Jose. You can buy a whole gallon of it at Wal-mart for $9.95

Do you have a Wal-Mart store in PR? If not, most auto parts stores have it.
If you buy it on eBay, the freight will eat your lunch.

[joeheli]

Yes , We do have have Wal-mart,Woman-mart, Man-mart,and expecially:DRUG-MART :D :D :D

[Chuck Irby]

Jose, you're too much! Have you been visiting the drug mart?

[joeheli]

Use to! I QUIT!

[Chuck Irby]

Good for you, Jose! That stuff doesn't mix well with flying, huh?