All things Rotax 582 Related

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Feeding your 582



Extracted from


Octane rating

We recommend using a "premium" type automotive fuel with an octane rating of 91, a minimum of impurities and little or no alcohols (maximum 5%).

Some may have noticed that the Rotax documentation specifies an octane rating of 90, based on the RON standards used in Europe. This is the equivalent of an 87 rating under the Canadian AKI standards. A rating of 87 is indeed considered "regular" fuel, but we still recommend a "premium" fuel for two reasons:

  • First, when fuel is premixed with 2-stroke oil, the octane rating is reduced by about 2 points. An 87 octane fuel would therefore become 85 octane.
  • Second, fuel evaporates and loses its octane rating when it lays in your aircraft's fuel tank or in a plastic jug. A "premium", 91 octane fuel will see its octane rating reduced to unusable levels after as little as three weeks. Fuel with a lower octane rating would obviously have an even shorter usable life.

Too low an octane rating will create detonation and pre-ignition which can damage the piston crown and even melt a hole through it.


Where to buy

It is recommended to buy gas at the busier gas stations of the major oil companies, since their tanks are renewed often allowing the fuel to stay fresh and clean.


Certain fuels contain alcohols such as ethanol. These ingredients should be avoided since they absorb water which then creates corrosion inside a 2-stroke engine. They also have the effect of reducing the oil's lubricating properties. Rotax recommends avoiding fuels containing more than 5% alcohol.

Aviation Fuels

It is possible but not recommended to use 100LL AVGAS, since the the lead content will increase deposits in the combustion chamber and on crankshaft ball bearings, inducing premature wear. Its higher octane rating does not bring any significant advantage to the engine's operation.

To be avoided:

  • "Regular" fuel except if used with oil injection and burned entirely on the day of purchase;
  • "Premium" fuel which is more than 3 weeks old
  • Alcohol content of more than 5%
  • Diesel. You are not crossing the Atlantic in a Diamond Twinstar

Engine Lubrication

2-stroke oil specifications

Rotax recommends using a "super" two-stroke oil which corresponds to ASTM/CEC standards and/or API-TC classification. It is also essential to choose an oil which is designed for an air cooled engine even if you own a liquid cooled engine.

2-stroke oil type

For most Canadian users a mineral or semi synthetic oil is recommended.

Synthetic oil should only be used by those who operate their engine nearly every day. Even when shut down, air is constantly circulating through a 2-stroke engine; it is never sealed like a 4-stroke engine. Even though it has excellent lubricating properties, a synthetic oil does not effectively protect a stopped 2-stroke engine against corrosion: it tends to attract moisture and will run off the parts rather than leave a protective coating.


If you own an oil-injected engine, you simply need to keep your oil tank topped up frequently. Otherwise, it is necessary to premix your oil and fuel. The ratio is 50 to 1, or 2%. This means you would mix 400mL of oil in 20L of fuel, 500mL for 25L, and so on. Using more oil than recommended would not help your engine in any way: it will accelerate the formation of carbon deposits which will eventually break loose and accelerate wear.

Rotary valve lubrication

The oil used in the rotary valve lubrication circuit of liquid cooled engines (462, 532, 582, 618) should be the same 2-stroke oil used for primary engine lubrication.

To be avoided:

  • Oils whose label do not bear the above mentioned required specifications
  • Oils primarily designed for outboard 2-stroke engines
  • Mixing ratios other than 50:1


Gearbox Lubrication

Rotax recommends API-GL5 or GL6, SAE 140 EP or 85W-140 EP gear oil for gearbox lubrication. A synthetic type of oil can be recommended for this application thanks to the almost-sealed environment of the gearbox casing.

To be avoided:

  • Low quality lubricants which will deteriorate long before the recommended replacement interval (every 100 hours)


Cooling Liquid

For its liquid cooled Aircraft Engines, Rotax recommends a mix of 50% antifreeze concentrate without sulphates and phosphates, with anticorrosion additives designed for aluminium, and 50% distilled or demineralised water.

It is possible to use a higher proportion of water if you have overheating problems, but it is important to consider the effect on freezing point. The maximum ratios specified by the antifreeze manufacturer should not be exceeded since deposits may form inside the cooling circuit.

To be avoided:

  • Low phosphate and low sulphate antifreeze
  • Water which is not distilled or demineralised
  • Excessive mixing ratios

Spark Plugs

The recommended spark plugs are the NGK B8ES or BR8ES. The "R" denotes a resistance which helps suppress radio interference. The use of spark plugs with a solid tip, rather than the screwed-on tip, is mandatory. The latter can unscrew itself in flight and dislodge the spark plug connector cap, creating an ignition failure.

Spark plug gap

  • Allowable range: 0.4-0.5mm / .016-.020"
  • Optimal: 0.45mm / .018"
  • The gap can be reduced to its allowable minimum to help starting in very cold conditions

To be avoided:

  • Other spark plug models and other manufacturers' equivalents
  • Screwed-on tips
  • Unverified spark plug gaps


Torque Values


Tightening Torques for Rotax Aircraft Engines

Here are a few tightening torques you might need when performing routine maintenance on your Rotax Aircraft Engine. These informations and much more can be found in our Engine Maintenance Logs.

More more torque specifications, please refer to the relevant maintenance manuals and illustrated parts catalog.

  Torque Agent Notes Rotax 2-Stroke
Aircraft Engines Nm M8 Cylinder Head Nuts
(air cooled engines) 22 195 16 - torquehead.gif
Undo and retighten one at a time following the specified sequence: M8 Cowling Bolts
(air cooled engines) 14 125 10 Loctite 242/243   M8 Exhaust Manifold Bolts (447 only) 25 221 18 Anti-Seize Tighten progressively in a crossing pattern M6 Exhaust Manifold Bolts (618 only) 10 90 8 M8 Exhaust Manifold Bolts (all other engines) 22 195 16 M8 Intake Manifold Bolts (air cooled engines) 24 210 18 Loctite 242/243 14mm Spark Plugs 27 238 20 Anti-Seize On a cold engine M16 Fan Nut
(air cooled engines) 60 530 44 Loctite 221/222 Use fan holding tool. Tighten slightly then rotate fan. Repeat until fully tightened. M18 Gearbox Drain Cap 24 210 18 - Secure with Safety Wire M10 Engine Mounting Studs 38 335 28 Loctite 221/222   Rotax 4-Stroke
Aircraft Engines           Oil Tank Drain Screw 25 220 18 - Replace gasket ring and secure with Safety Wire Oil Filter Hand tighten - Oil gasket, retighten after test run Magnetic plug 25 220 18 - Secure with Safety Wire Water Pump Drain Screw 10 90 8 - Replace gasket ring Carburetor Socket Clamp torquesocket.gifTighten to a distance of 7mm/0.276" Carburetor Socket Screws 15 135 11 Loctite 221/222   Spark Plugs 12mm/16mm 20 180 15 Anti-Seize On a cold engine

Please, do not use red Loctite (such as type 262)! It is a permanent adhesive! It is sometimes very difficult to remove parts secured with it without damage.


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Attached is the Operators and Installation manuals along with the Repair manual in 4 parts. The repair manual doesn't go in order. Just open up each document and push Ctrl+F and type in a key word you are looking for and it will instantly search the whole document for you.

582 Operators manual.pdf

582 Installation manual.pdf

582 Repair manual Part 1.pdf

582 Repair manual Part 2.pdf

582 Repair manual Part 3.pdf

582 Repair Manual Part 4.pdf

Visual inspection.pdf


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Rotax 582 Tuning


Stock Jetting

                                                                 Main          Idler        Needle jet       Needle     Clip from top          Air screw

Rotax 532/582 DC                                   165             55              2.72              11G2               3                   1.0 turn out


By Jerry Olenik of Green Sky Adventures


As promised, I am going to go through some things that may help with
properly tuning the 2-stroke aircraft engine.

No matter who makes the engine, the first thing I do is lean the idle
mixture. Even if you think you have a smooth running engine at idle,

you may still get problems at other power settings from excessive fuel

that loads up or even harmful long term effects like excessive carbon build up.

Often people go changing main jets or needle clip positions because of

fowling spark plugs or whatever when the problem is really coming from a rich idle.

Most of the time with a 2-stroke, you can not lean to peak efficiency like
in a Cessna or the like because the engine will seize before you get there.
However, at low engine speed you CAN lean to peak efficiency without
damaging the engine. To do this, I would suggest securing the airplane so
it can't roll away, because as you lean the mixture, your idle speed is
going to increase and may increase enough to make the plane roll away.

Once appropriate measures are taken to secure the plane, start the engine
and listen carefully at idle. Listed for occasional bumps or misses.
Listen to the general tone of the engine. Feel the airframe for vibration.
This is sort of like tuning a guitar by ear. Then shut it down. The 2SI
engine really is usually a smooth running engine at idle even when it's too
rich, so you may have to go by RPM more than the smoothness. RPM will
increase as you get closer to peak efficiency. With the Bing 84 carb or
Bing 54 carb, start turning the idle air screw out (counter-clockwise) about
1/2 turn (180 degrees). This would be the smaller screw that is recessed
into the carb. Turning it out allows in more air and effectively leans the
mixture in the idle RPM range. As you turn it out, keep track of how far
you have gone. After each half turn, start up the engine and listen and
feel for bumps, misses, roughness and the general tone of the engine.
Generally a deeper tone will be richer and a higher pitched tone will be
leaner. Continue to go through this until the engine seems to be running
completely smooth. As smooth as glass. Note where you are on the air screw
adjustment at that point.

One thing you may run into is that you could run out of adjustment on the
airscrew. If you turn it out far enough to see the o-ring that seals it,
you need to go to the next leaner idler jet. If you change to a leaner
idler jet, start out with the airscrew turned out about 1/2 turn and
continue with the process. Even if it seems like it is smoothed out, note
that setting and continue. You will eventually get to a point where the
engine will decrease in RPM and/or die or not want to run. Note that point
as well. I would then set your idle air screw about mid way between where
it seemed to totally smooth out and where it was too lean to run. That way
you should not need more adjustments with changes in the weather or density
altitude unless those changes are severe.

Now that you have your idle set, you are ready to try your mid range. NOTE:
leaning the idle can sometimes have some effect on the midrange and you may
want to start out in the richest (lowest clip position) needle setting until
you know where your EGT is going to be. With the engine properly warmed up,
increase the throttle into the 4000 - 5000 RPM range. Make movements with
the throttle watching your EGT for the hottest spot and just make a mental
note of where your engine has it's hottest EGT. Be cautious about staying
within limits on all your temperatures because now you are running at engine
speeds that can cause damage if mistakes are made.

For reliability and engine longevity reasons, I take exactly the opposite
approach to mixture at higher power settings as I do for idle mixture
settings. What I mean is that I like to make the mixture rich until it runs
a little bit rough, then lean it out a little from there. This is just the
opposite that you would do a in Cessna or other GA type aircraft. While you
are searching for that hottest spot in your mid range, keep your ears open
for any little misses or bumps, and feel for any momentary waves of
vibration in the airframe. Those are all signs that the mixture is
bordering on being too rich. The reason you are looking for the hottest
spot in your EGT is so that you don't make an adjustment that would put that
over limits. Each position on the jet needle will change the mid range EGT
approximately 50 degrees + or -. If you don't notice any roughness or other
signs of being too rich in the mid range. Make it a little richer. If you
are already in the richest position on the jet need and well within temp
limits, you might just leave it alone here. Otherwise you would need to go
to a different needle jet to make the mixture richer. If the mid range is
rough and acts like it is rich and you are well within limits on your EGT,
you can move the clip to the next leanest position. When leaning the
mixture always make small incremental changes because too lean will cause
damage often without warning. So if your EGT is 900F or 1000F and the
engine is running rough in the mid range, try moving to the next leaner
needle position. Do this until either the engine smoothes out in that range
or you come within 50F of your upper EGT limit. If your EGT limit is 1200F
and you are at 1150F, you probably do not want to make another adjustment
any leaner.

Once the mid range is set, with the engine properly warmed up, you can do a
static run up to full power. Make a note of the maximum RPM and the EGT.
If your engine makes its rated power at 6000 RPM, you maximum static RPM
should usually be a little less than that. How much less really depends on
how fast the aircraft is because that max RPM will increase during flight.
So if you have a relatively slow aircraft with an engine that makes it's
rated power at 6000 RPM, you might expect to set your maximum static RPM to
5800 or so. If you have an engine that makes it's rated power at 6500 RPM,
you might set your maximum static RPM at 6300 or so. So if you are not
close to that, you should make a propeller pitch adjustment to load the
engine properly. If you do have to make a large change in propeller pitch,
it will also have an effect on your fuel-air mixture throughout the entire
RPM range of the engine. So if you were loaded to 6300 and had to make it
5800, your mixture is going to get richer. If you were loaded to 5800 and
you need to change it to 6300, your mixture is going to get leaner. So
after adjusting your pitch, it is a good idea to go through the carb
adjustment process again.

If your full power EGT is fairly low, like in the 800 range, that may also
be having an effect on your full power output. Generally, you want the full
power range to have a lower EGT than the mid range for added protection
under the higher stress conditions, but if it is too much lower, the engine
will not perform. If your EGT seems to be very low at full power, and the
engine seems to bog down, you may need to change to a leaner main jet. The
main jet is the only part of the carburetor that has control over the full
power mixture. At full power, the jet needle is all the way out of the jet
and a needle adjustment will not change this setting. The main jet,
however, WILL have some effect on the mid range mixture. So if you change
to a leaner main jet, it is always a good idea to change the needle clip to
the richest position on the needle for the first run up. You can always
make the mixture leaner in the mid range if its too rich, but if it's too
lean, you might need a new piston.

Since mixture effects the power output of the engine and propeller loading
effects mixture, this process is sort of like hitting a moving target in
some cases. If you find that you have to make a large propeller adjustment,
you may have to go back and forth through this a couple of times. Once set,
and set properly, however, you should be able to enjoy many hours of
enjoyable, trouble free use. If you don't set the engine, carbs, and
propeller up properly, you will likely have many hours of problems,
frustration, and may even cause damage to the engine and/or airframe.

These are the exact same steps I use when setting up an engine on a
customer's aircraft weather the engine is new or used. My customers are
usually very pleased with the results since they no longer have to put up
with the vibrations and throttle response problems that they just took as
normal before. Hopefully you guys can get the same results.

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HACman info


Hacman install in a 582 powered Avid




HACman Mixture Control
By Gerald J. Olenik,
Pres. Green Sky Adventures, Inc.


Why worry about jetting and mixture?

The need to adjust fuel/air mixture with changes in air density is nothing new. Air density varies with altitude and with daily or seasonal climate changes causing our engines to run richer or leaner..  An operational symptom of a fuel rich engine is rough running. Conversely, too lean a mixture results in very smooth running, often preceding piston seizure on 2 strokes.  So, what's better, too rich, (rough) or too lean (dead)?  Neither of these are very attractive, but you must admit, a rough engine is better than none at all.

Wait a minute. One might ask. Why such extremes? Isn't there some compromise or middle ground? . Of course there is! Bing 54 carburetor equipped,  2 stroke aircraft engines, allow a relatively broad operating range before a change in jetting is required.   If your engine is jetted for the middle of that range, as with standard jets, and you don't fly higher than a few thousand feet or in extreme cold or fast, quite possibly your engine will never be so rich that it runs rough or so lean that it seizes. Two variable components in the mixture equation, other than the carburetor are Load and Air Density. Changing either of these will cause an engine to run richer or leaner. It won't necessarily run badly unless drastic changes are made in one of these components or there are multiple changes.

Variable 1:  Correct Load                                                                      
Let's say we have a  65 HP 2-stroke engine that makes its maximum power at about 6,500 rpm, with Wide Open Throttle, (WOT) in standard atmosphere, (sea level, dry air, 59° F, 29.92" hg pressure).  That is an exact condition that compliments  standard carburetor jetting.  So, "correctly" loaded, at standard atmosphere,  most any throttle position will result in a fuel / air ratio that is not to lean, not to rich,  ...Somewhere in the middle. As airspeed increases, the load typically decreases allowing higher rpm for any given throttle position.  Fast is a relative term, but for this argument, it is any speed that lightens the load on the engine allowing its maximum WOT rpm to substantially exceed 6,500. The extra RPM is not the enemy,  its a messenger, telling a pilot the fuel air ratio has drifted from the middle, towards a potential enemy (the lean side).  If a pilot responds by reducing the throttle position to reduce rpm, the messenger is silenced, but the engine is still gulping extra air. It's at a different  throttle position but still running leaner than it would without the lightened load.
So, in the case of faster aircraft, the carburetors may need changes from  standard jetting to richen the mixture. Or, another approach is loading.  Instead of a propeller that allows 6500 rpm at WOT static, how about one that allows 6500 rpm  at maximum speed in level flight? This should result in a mixture within safe operating range at any throttle position during flight. Either change will make the mixture a little on the rich side for static operation. That shouldn't be a problem as long as there isn't too much variation in atmospheric conditions.

Variable 2: Air Density
Regardless of the choice in tuning method, there remains that major variable, Air Density.  We may occasionally operate at standard atmosphere, but not often or continuously. Standard Atmosphere, (could also be called "Standard Day",) is basically a benchmark for reference, that can be described as: sea level elevation, dry air, 59° F, 29.92" hg pressure. It actually calculates to 1 ft density altitude. Density altitude, therefore, is a useful value that quantifies the effects of  temperature, pressure, and humidity on our engine and aircraft. It can be a little confusing, because high density altitude  = less dense air, and low density altitude = more dense air.
In the example above, where jets were enlarged, or load was increased  to achieve proper fueling in flight, it was satisfactory to be a little rich statically.  However, if density altitude increased by 4 or 5 thousand feet, the mixture may not work at all. You may occasionally witness this, watching an aborted take off of a Northern flyer, at Sun n Fun's Paradise City when  outside air temps get up near the nineties. I can't be the only one who's ever had this happen! The engine makes a lot of intake roar, at WOT, but only about 30% power.
What about the other side of the coin? If we were cautiously tolerating a lean mixture, perhaps on a long cross country where some high altitude flying may be necessary, couldn't the DA decrease by 4 or 5 thousand feet as the flight progresses? On Two Strokes, that could drive an already lean mixture to the seizure point.

You don't even have to leave home to have such wide variations. During tests of our High Altitude Compensation kit on a Kitfox Model II, we flew to 10,000 feet msl on one particular day.  That day, the density altitude was 2,038 ft msl at our departure point.  Two days later, the weather was ideal for more testing, because  a cold front had passed bringing DA down to 1960 ft below seal level.  That's a 4,000 ft change, absolutely enough to drive an already lean Two Stroke to the seizure point.   Obviously, monitoring EGT is essential, as it is the best readily available method of  knowing what's happening with the fuel air ratio.

Mixture Control
The High Altitude Compensating system for Bing Carburetors came on the scene about twenty years ago. Design and testing on the (discontinued) automatic system goes back to the late eighties.  On an early "proof" flight, the crew from Robertson B1RD company flew a HAC equipped, Rotax 532 powered,  B1RD to over 20,000 ft. while maintaining proper mixture. Green Sky Adventures, Inc., has tested HAC carburetors on six different Rotax engines over the last fourteen years on the company's Zippy Sport. From speeds of 40 mph to 130 mph, from sea level to 15,000 plus feet, the system can easily maintain EGT within operational limits on both 2 and 4 stroke application.
Initially, High Altitude Compensation was available only as a complete package which not only included the HAC chamber, lines, and fittings, but also came with two (one if single carb configuration) complete Bing 54 carburetors, and two application specific Rotax/K&N filters, all at a price of around $700! Around 2001, Green Sky Adventures, Inc. put  HAC technology into a much more affordable package which, in most cases, eliminates the need to replace existing carburetors or airfilters.


The basic kit includes: HACman controller, Fittings, Lines, Clamps Jets, and detailed installation instructions. Pictured above is HACman TC-64 for Bing 64 carburetors used on HKS-700e and Rotax 912 series Four Stroke application. Price range $160 - $200


Bing 2-Stroke: Late model 2 stroke Bing 54 36 mm carburetors (right) are equipped with an extra passage to the venturi, which is connected as a source of low pressure, via a flexible hose, to the HACman controller.


Here's how it works

Did you ever wonder what makes fuel flow up the jets, from the carburetor float bowl, en route to the engine? Is it vacuum at the venturi?  That's not quite descriptive enough. It is better defined as a differential pressure between the float bowl and the venturi. What's the pressure in the float bowl? Here is an important hint, the bowl is vented to outside atmosphere. So, it should be the same atmosphere, or ambient pressure, that's feeding the airfilter.  If it is not,  the differential between the venturi and float bowl is going to change and so will the mixture...Maybe richer, maybe leaner. Just think of that for a second. If  fuel air mixture can be thrown off, accidentally by improperly venting the the float bowls, why not control the venting to effectively control mixture? That's exactly what a pilot can do with a HACman equipped powerplant.  If  pressure in the float bowl is reduced, relative to the venturi,  less fuel makes its way up the jets, and consequently, mixture is leaner.


Think of the  HACman controller as a meeting room where airfilter (ambient), float bowl, and venturi pressures accumulate for management. Let's call this an accumulation chamber. With HACman in full rich position, float bowls are exposed only to ambient pressure, exactly as if there were no mixture control at all. As the HACman precision needle valve is opened, ambient pressure within the accumulation chamber and consequently the float bowls is reduced by feeding it to the venturi via a connection on late model Two Stroke Carburetors. The amount of ambient pressure reduction is controlled by a tapered needle which changes position as the controller is turned clockwise for rich and counterclockwise for lean.  The greater the pressure reduction, the leaner the mixture.
As exposure to low pressure is shut off, float bowl pressure returns to ambient, and the mixture goes as rich as the jets will allow. With HACman Two Stroke installations, standard jetting starts out several steps richer. This is why we say the default, or failure mode is typically toward the rich side. If the low pressure line is blocked, or comes off, float chamber pressure returns to ambient and mixture goes rich.

Are there potential risks? The down side
Hypothetically, at 18,000 feet, a loss of the low pressure line, whether blocked or broken, could result in rich enough mixture to kill the engine.  At half that altitude, it would run rough and loose a few hundred rpm. If the vent or static lines fail, the location and type of failure would determine the change in mixture..
Even though mixture adjustment is steady and incremental with HACman, the pilot can control it and must be knowledgeable of that process or the consequences can be dire.  If you have guest pilots or students, HACman can simply be left in "your take off" position and the engine will behave exactly as if mixture control were absent from the powerplant.

What does the High Altitude Compensation really do for me? The up side
We all have our preferences about what and how  we fly. Here are a couple of mine.
My first preference is for airplanes that can be flown at all normal attitudes, throughout their speed range, at any and all throttle positions, without quitting  (exceeding EGT limits, upper or lower). Particularly, on 2 Strokes, in pursuit of that preference, there is a tendency to overload, and/or over fuel.

My second  preference is to reduce exposure time to hazardous terrain, just in case I don't get my first preference.  I agree, "Low and Slow, Way to go..." but occasionally it isn't the way to go. There are those flights that take us over hazardous terrain. ...Areas where there is just no attractive landing site. Sometimes flying high, is like pushing the fast forward button to a safer place. With a 65 knot cruise speed, if a 12 knot headwind can be converted to a 15 knot tailwind ground speed increases by 50 percent. Even if it takes 9,500 ft to do it...why not?
On the Kitfox Ohio/Florida trip mentioned above, it was not a hypothetical. One leg between Parkersburg WV, and North Wilkesboro NC was definitely over hostile territory.  The engine was tuned perfectly on the cool September morning  for preference number 1 at the departure point up by Lake Erie.  By mid day over the mountains of West Virginia, the engine was beginning to exhibit rich symptoms at 4,500 feet and there was a quartering headwind.  The wind at 9,500 would have been almost 20 knots on the tail, but lack of  mixture control sentenced the flight to lump along, low and slow. This allowed plenty of time to reflect on how badly I wished this plane had the HAC kit.

Automatic vs Manual
Some of you may think you're having dejavu all over again. A while back, I wrote about mixture control and an automatic system. At the heart of that system was a sealed chamber and metering device. Once upon a time, these chambers were mass produced by BING for another industry whose technology has evolved beyond their requirement. Eventually supply of the automatic chambers was exhausted. Without high production levels, the price is prohibitive and there is no plan to continue.
When we set up our first auto HAC system it took only a few hours to realize, although it gave our engine the ability to automatically maintain mixture regardless of density altitude, the wide speed range of our test bed could still allow light enough loading, to send EGTs to the seizure point. The auto HAC was doing it's job. Our job was to set up the carburetors rich enough that no throttle position, airspeed, or attitude would allow excessive EGT. Eventually that perfect combination was achieved and our aircraft could be flown and maneuvered by others without worries of EGT related  piston seizure, hot or cold, high or low, fast or slow.  This is "the cowardly technique of two stroke tuning", just on the smooth side of too rich.
In maneuvering, rudder, aileron, elevator, and throttle controls  may touch their stops numerous times within just a few minutes. Each input can change engine loading and mixture. That is why "the smooth side of too rich" works so well for maneuvering flights
Light sport planes beg to be maneuvered and the cleaner they are the faster they go. The faster they go, the more potent they become for cross country flying. To be absolutely clear, engine failures on cross country flights have been just as annoying for me as the ones at home. However,  there is a different mind set for long cross country. The maneuvering becomes much less of a factor, replaced by hours of navigation, weather, airspace, collision avoidance, and  fuel management. During a long cross country, the throttle may reach it's stops twice, opened on take off and closed on landing. ...The elevator, once on landing. Quite possibly the remaining controls will move a small percentage of their available travel. Hours may pass without a single throttle adjustment.
On one occasion,  I wanted our Zippy Sport test bed to fly me to Northeast Ohio from Florida. ...A jagged 2 day trip with an overnight  in Jacksonville, NC to visit family. The first day, I had to divert, missing every planned fuel stop. My calculations were based on an average fuel burn of 4.5 gph on the Rotax 582, planning 2 hour legs allowing  2 of the 11 gallon capacity as reserve. My calculations were wrong,  The automatic mixture kept EGTs as normal as ever, but because of my "cowardly technique of 2 stroke tuning" normal was in the lower part of the operation range 930 to 1150 degrees F. I can recall watching the fuel level decrease while that 582 hummed along so smoothly and the EIS reported EGTs of 1025. Another 100 degrees could have been a real range extender.
The following morning, I weighed the pros and cons of taking  time to change needle clip positions but elected to leave it alone.  Within a few hours, I was glad of that decision. The weather had gotten down to marginal. A fairly benign system consisting mostly of continuous light rain and low ceilings stretch pretty much along the mountains from southwest to northeast. From Danville, Va. I only had to get northwest of Becky WV to be in the clear but that was the roughest terrain and darkest weather. The system looked like it petered out to the north east and so does the terrain, to a great extent. So northeast it was. At Cumberland, the weather and terrain had mostly subsided. One good decision was not to change those needle clips. This was a stretch of cross country that was definitely not boring and included both maneuvering and throttle position changes. The last thing I needed was to worry about leaning out while changing power.
That describes both days of a two day trip. The first day would have went better if the mixture was leaner. If the mixture had been leaner, the second day may not have work as well.  In either scenario the ability to change mixture in flight, manually could be a valuable capability.

After organizing components to produce the auto HAC, and developing  interest at the market place, it was frustrating to loose supply of a major component of the kit.  I used to keep a list of "harebrained ideas", as my father would call them, hanging on the wall of our shop. It was around the time of our first auto HAC experiences when that list was annotated. "develop a manual mixture system based on auto HAC principals". It only took ten years to gather the motivation to act on HACman. This technology dates back to the early days of aviation. So, it's not an invention, but none the less necessity has been a close relative of the HACman development.


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Thanks Joey, it's an oldy but a goodie.  Thanks for compiling the info in 1 place for us. I'll read through it all. 

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The California Power Systems 2-Stroke tech articles right above this thread will keep you learning for days.

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Here's another good source of info for you guys flying behind a 582.

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Thanks for the TOs Joey. Have read the HACman info several times. Just ordered the kit for my 582.  Flying my KF III this summer, I had a couple density altitude days over 6000 feet. Field elevation at Fallon Municipal is 3948. It performed ok, but any little bit will help. Anyways thanks for the tech orders.


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