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Products - Frequently Asked Questions (FAQ)

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My brand new 2-stroke ABC engine is very hard to turn over by hand. It seems to 'stick' at one point and I can't turn it past that point without using a lot of force. Is something wrong?

An ABC-type engine has an Aluminum piston, and a Brass Liner that is plated. Traditionally, the plating was Chrome, but some engines use a different metal, usually a nickel alloy.

An ABC engine's liner is tapered towards the top. This causes the piston to "grab" as it moves towards Top Dead Center (TDC) when the engine is cold. (Some engines will actually seize if you turn them over when cold, requiring considerable force to turn them through TDC.) When an ABC engine is run, the heat of combustion causes the metal parts to expand. Because the piston and cylinder liner are made of different metals, they expand at different rates. The liner expands just enough to make a nice fit for the piston once the engine warms up. The liner is tapered because the cylinder is hotter near the top. The different temperatures cause different amounts of expansion, making a perfect fit when your engine is at optimum operating temperature.

You may interpret what you feel as play in the connecting rod. This is almost never the case with a brand new engine. What you are feeling is a slight springing of the connecting rod as you force the engine through TDC. The piston doesn't go all the way to the top, causing the rod to flex slightly, which gives an "over the center" feeling. Many people have interpreted this as play in one of the rod ends, but it is not and is perfectly normal.

How do I break in my new ABC engine (for example, GS45 ABC)?

Your ABC engine must be broken-in at full throttle. You don't want to run it too rich. Too- rich running will not allow it to warm to proper temperatures, so the liner does not get properly seated. Lean it until it is running just out of what is known as "four-cycle" mode, then gradually work leaner with each run. You can lean it to peak RPM as soon as the engine will accept it.

You should prop your engine to allow higher RPMs. ABC engines work better at higher RPM. You should also use a fuel that contains castor oil in the lubrication mix. Castor oil helps the engine run well and is the better lubricant for our ABC engines. All-synthetic fuels have been known to cause difficulties in running at times.

Once properly broken-in, your ABC-type engine will serve you well and deliver lots of reliable performance.

What types of fuels should I run in my giant scale SuperTigre engine (ex: 3250)?

(Important note: The G2300 (G20/23) is NOT considered a "Big ST" and must not be run on fuels lower than 18% oil.) Once your BIG SuperTigre has a gallon or two of regular fuel run through it, you can use one of the so-called "SuperTigre", "ST" or "Super-T" fuels, which have 10%-12% oil content. Keep Nitro 10% or lower for best operation. We use an O.S. #8 or the O.S. Type F glowplug. We recommend you try both to see what works best for you.

To properly set up your carburetor to run these types of fuels, follow these steps:

  1. Set the spraybar so that the fuel slot is pointed straight down the center of the carburetor. You will have to look through the carb from the bottom, with the venturi fully open. Loosen the two screws next to the high-speed needle valve to rotate the spraybar so that the slot is centered.
  2. The idle needle can be seen in the slot of the spraybar. It looks like a piece of wire that has the end squarely cutoff. Set it less than halfway across the slot when the venturi is fully open.
  3. Open the high-speed needle about 2-1/2 to 3 turns out from closed.
  4. All of these settings are very rich. Start the engine at about 1/4 to1/3 throttle. Once the engine starts, advance the throttle to full. You can then lean the high-speed needle until the engine is running just rich of peak RPM.
  5. Once you have the high-speed needle set, retard the throttle a bit and use the idle needle to adjust the engine. Retard a bit, and adjust. Keep doing this until you reach the desired idle RPM and mixture. Remember, since we started out with an intentionally-rich setting, the idle mixture will have to be leaned.
  6. Finally, the midrange is adjusted by rotating the spraybar a hair. Just loosen the two screws next to the high-speed needle and rotate the spraybar just a tiny bit. Either direction is OK. This will help you get a good transition and midrange.

I want to change the bearing in my out-of-warranty engine. How do I do this?

We recommend you send your engine in for service rather than attempting to change your bearings yourself. If you've got a blown bearing chances are good your engine has suffered other damage as well which you might have missed. However, if you're REALLY comfortable working on engines, these steps will assist you in changing your bearings. If you are unsure how to complete any one of these steps, we caution you against disassembling your engine and recommend instead that you send it to our warranty and service center for non-warranty repair.

  • Remove carburetor from engine.
  • Remove rear cover and cylinder head.
  • Slide cylinder liner straight up.
  • Remove piston/connecting rod assembly from the crankshaft. Pay attention to the orientation. The assembly has a definite front and rear.
  • Remove prop nuts, prop washer, and drive washer from the front of the crankcase. Remove crankshaft by sliding it straight out of the back of the crankcase.
  • The crankcase must be heated to remove the ball bearings. You can heat the engine in an oven. Put the engine on a cookie sheet and place in an oven set to 250 degrees. When the engine has reached that temperature, hold the engine with an oven mitt and gently rap it against a piece of wood. The bearings should fall out.
  • Let the crankcase cool.
  • Clean the crankcase thoroughly.
  • Reheat the clean crankcase in the oven until it's hot.
  • Gently install the new bearings (not heated) by tapping them into place with a piece of dowel rod. Don't use a hammer or steel rod as a driver. The bearings will slip easily into place if they are inserted straight.
  • Let crankcase cool.
  • Reassemble the case in the reverse order of disassembly, and use plenty of oil when assembling the engine. Automatic transmission fluid makes an excellent assembly oil.

If you need further help, you may want to consult modeler's engine books such as those printed by Model Airplane News or Harry B. Higley & Sons, Inc.. They have comprehensive pictures and explanations on model engines.

This engine seems to smoke a lot. Does that mean I am running it too rich?

Not necessarily. If the engine is now smoking more than it has in the past, and everything else is exactly the same (same fuel, plug, conditions, etc), then your engine is probably running a little more rich than it has previously. But the amount of smoke is not an absolute indicator that an engine is running overly rich. Different fuels will smoke differently when the engine's properly-adjusted. Get the engine adjusted properly, and then see what kind of smoke trail you get. If the fuel smokes a lot, even though the engine's running well, your fuel has an oil that encourages smoke. Don't worry about the amount of smoke output, and never sacrifice your engine's oil intake just to minimize the 'vapor trail' it leaves in flight.

Why did my prop come off my 2-stroke engine?

With almost all R/C model engines, the direction in which the propeller nut tightens keeps the propeller nut from loosening when the engine is running. The direction of the power pulses tends to tighten the nut. It's very possible that the nut became loose when the engine backfired during starting. Backfiring is a sign of flooding or other deficiency in starting technique or a problem with the engine.

The most common reason propeller nuts become loose is that they were not tightened enough. Instead of using a "4-way" wrench to tighten a propeller nut, you may use a six-inch box wrench or adjustable wrench for propeller tightening. We use both hands and arms to tighten the propeller nut onto an engine, with propeller held in one fist, with the wrench in the other. We apply enough force that it takes both hands to loosen the propeller later. When it's properly- tightened, we have rarely seen a propeller loosen itself on a small 2 stroke engine.

I heard about a new product which is not yet listed on your web site. How can I get more information?

If a product is not yet listed on our web site, chances are good that we do not yet have information on that newly released product. Please visit your favorite hobby shop and our web site regularly for new technical information as it becomes available.

How much faster will my model be if I change my engine X for a SuperTigre engine Y?

Unfortunately, we cannot estimate the running speed of your model, even in attempting to compare one engine's performance to another. Speed is dependent on a large variety of factors, including including props and fuels, engine break-in, altitude, fuel and plug, assembly accuracy and, of course, pilot skill.

What temperature is ideal for my engine?

It's not possible for us to give you an actual temperature or temperature range for your engine. The specific temperature is determined by too many factors. There is only one way to determine at what temperature your engine should be run - get it running just how you like it, then find out what temperature the engine reaches.

Make sure your engine is operating properly and providing the performance you expect. Be sure you are not overly lean and shortening your engine's lifespan. Use the exact setup every time...fuel, exhaust system, plug, measurement location, and so forth. If you change anything, the temperature will change. Once you have the engine running the way you want it, take your measurement. You will have to take measurements over time to find out how the weather affects it. As the air temperature and humidity change from day-to-day, the operating temperature will change. Eventually, you'll find a temperature range that you can use.

Engine temperature is not an absolute number for setting your engine. It is only a guide, and can help alert you to potential problems. The only sure way to make sure your engine is running correctly is to see how it's running. An engine can be operating at "correct" temperatures, but not running well, or seem to be running "hot" or "cold" yet is performing flawlessly.

Finally, use any temperatures you read about, or people tell you, as rough information. The only useful numbers are the ones you actually measure when your engine is running correctly. If your engine is running correctly, then what you measure is correct, even if some else says it's too high or too low. Don't worry about the differences. Each engine is in a unique installation with a unique set of circumstances, so there can be wide variances in engine temperature.

Can you provide me some basic instructions on tuning my smaller (less than 120 sized) SuperTigre carburetor?

To properly set up your carburetor, there are a few steps...

Make sure the spraybar is set so that the fuel slot is pointed straight down the center of the carburetor. You will have to look through the carb from the bottom, with the venturi opened to full. Loosen the two screws next to the high-speed needle valve to rotate the spraybar so that the slot is centered.

The idle needle can be seen in the slot of the spraybar. It looks like a piece of wire that has the end squarely cutoff. It should be less than one-half way across the slot when the venturi is opened to full.

The high-speed needle should be opened about 2-1/2 to 3 turns out from closed.

All of these settings are very rich. You'll have to start the engine at about 1/4 to 1/3 throttle. Once the engine starts, advance the throttle to full. You can then lean the high-speed needle until the engine is running just rich of peak RPM.

Once you have the high-speed needle set, you can retard the throttle a bit and use the idle needle to adjust the engine. Retard a bit, and adjust. Keep doing this until you have reached the desired idle RPM and mixture. Remember, since we started out with an intentionally-rich setting, the idle mixture will have to be leaned.

Finally, the midrange can be adjusted by rotating the spraybar a hair. Just loosen the two screws next to the high-speed needle and rotate the spraybar just a tiny bit. Either direction is OK. This will help you get a good transition and midrange.

My airplane does not have as much vertical performance as I would like. What can I do?

Prop selection is absolutely critical in determining if your model will have a lot of top end speed or a lot of vertical performance (ability to climb straight up). The same airplane with the same engine, fuel, etc, can change DRAMATICALLY just by changing props. It is very much like shifting gears in a manual transmission automobile—high diameter low pitch props are like low gear - they have tons of pulling power and the plane will have good vertical performance relative to a low diameter high pitch prop which provides lots of speed and momentum but very little pull.

One important note: a high diameter low pitch prop at very low RPMs acts like an air brake - just like putting your car in low gear and dumping the clutch to use the gearing to slow the car down. So if you are just starting to experiment with low pitch props, be sure to practice landing approaches with some altitude so you can get a feel for how quickly pulling your throttle back to idle will slow the airplane.

Your engine specifications give a BIG range of props. How do I know what is the best prop for my airplane?

Prop selection is absolutely critical in determining if your model will have a lot of top end speed or a lot of vertical performance (ability to climb straight up). The same airplane with the same engine, fuel, etc, can change DRAMATICALLY just by changing props. It is very much like shifting gears in a manual transmission automobile—high diameter low pitch props are like low gear - they have tons of pulling power and the plane will have good vertical performance relative to a low diameter high pitch prop which provides lots of speed and momentum but very little pull.

One important note: a high diameter low pitch prop at very low RPMs acts like an air brake - just like putting your car in low gear and dumping the clutch to use the gearing to slow the car down. So if you are just starting to experiment with low pitch props, be sure to practice landing approaches with some altitude so you can get a feel for how quickly pulling your throttle back to idle will slow the airplane.

I used to own product X. I can't find it on your web site now. Do you still make it? If not, will you produce it again?

If the product you are seeking is anything other than an accessory or repair parts for another item, then unless a product is brand new, if it is not listed on our web site then the product is no longer produced. Unfortunately, we cannot answer whether or not a product will be reproduced in the future.

I am building a twin and want my engines to spin their props in opposite directions. Does ST produce an engine with a counterrotating crankshaft?

No, ST does not offer an engine in this format at this time, and a standard engine cannot simply be 'reversed' in any means. However, you could go to a gear reduction system for both your engines with the reverse direction engine having one more or one less gear in the gear train. However, we are not aware of anyone who makes a product specifically for this task.

How do I know how to set the air bleed screw on my engine?

Always follow the printed instructions for your engine. As a general guideline: As the air bleed screw won't affect the way the engine runs with the throttle barrel more than a couple of mm open my suggestion, turn the screw all the way in until it stops (DON'T over-tighten it). This will give you your maximum rich idle mixture. Now set your high-speed needle as instructed in your manual.

You can then back out the screw a little at a time. In order to see if you have too rich or too lean an idle mixture, pinch the fuel line closed with the engine idling. If it speeds up noticeably immediately, then the mixture is too rich and you need to back the screw out some more. If the engine dies immediately, the mixture is too lean. If it idles steadily for a few seconds, then speeds up, then dies, it is just right. Between each adjustment run the engine at a high throttle setting for 15-20 seconds or so to clear out any excess fuel which will make it harder to determine the correct needle setting.

(Remember that the high and low needles affect one another so you will need to work back and forth between them to get a perfect running engine.)

I have an older engine with a good bit of time on it. I am using fresh fuel and plugs, both of which I know to be good from running in a different engine. When I start it up I have to run it very rich or it will run hot and seize. After two tanks of fuel have been run through rich I lean it up and it runs great the rest of the night. What could be wrong?

Your engine may have varnish buildup to the point that it is worn out. The varnish buildup will cause the clearances to be too close so that immediate leaning will cause the parts to start to seize, but rich running will lubricate it enough until it warms up. When the engine warms up, it expands enough so that the parts plus varnish have OK clearances. If the engine is devarnished, it may not run well at all due to the wear from the varnishing.

I am thinking of installing an engine inverted. What do I need to know?

There are a few things to know about the nature of setting up and running any engine inverted. RC engines are small, lightweight and fairly simplistic engines. They do not have all the complex equipment available to competition aerobatic full size aircraft engines or similar machines; therefore, when asked to run in inverted mounting, sometimes they can be a bit more challenging to set up than an upright installation.

First, realize that your engine may be full of fuel PRIOR to starting, risking hydrolock which can do severe damage to your engine, especially if the aircraft has been stood on its nose or even just nose low during transportation. Always flip the prop over to check the compression prior to using a starter. If it seems harder than normal, remove the glowplug and flip through several times or spin the engine with an electric starter to clear it and avoid the possibility of hydrolock.

Next, ALWAYS follow your manufacturer's instructions on engine break-in. In almost every case, the engine should be broken in on a test stand where it can be properly watched, cared for, fueled, drained, and adjusted easily and safely. If your manufacturer recommends in flight break-in, just be aware that it will be soft on power until the break-in period is completed and always be prepared for a dead stick landing during those break-in flights.

Then, once it is broken in, it can be installed. Please note that it is best to try to locate your engine so that the needle valve is in line with the centerline of the fuel tank if possible.

In some cases tuning in the inverted installation is a little more challenging due to the tank/carb relationship combined with the inverted mounting. If this is the case, tuning with the aircraft inverted/engine upright will help get the engine running flawlessly, then it can be run inverted.

Finally, some engines, especially inexpensive bushinged budget engines, will not like to start in an inverted position, again due to carb/tank positioning and fuel flow. In those case, you may need to start the aircraft inverted and turn upright to fly when running.

Can I use your aircraft/heli engine in a ground vehicle? If so, where can I purchase parts to allow me to do so?

We cannot recommend or support this, as engines for car use and boat use are designed very differently and have very different cooling supplies than an aircraft or heli engine.

I am interested in using a 3-or 4-bladed prop for a more scale appearance. How do I decide what size prop to purchase?

Please be aware that 3-bladed props are less efficient than a 2-bladed prop, so you are going to lose some performance. Additionally, 4-bladed are less efficient than 3. If your model is already marginal on power on a 2-blade, we strongly recommend against a 3-blade prop.

If, however, you have plenty of power and are willing to give up some performance for scale look and sound, then a 3-bladed prop is for you. You will want to start with a prop with either 1" less diameter or 1" less pitch than your 2-blade prop as a rule of thumb. For example, if your engine happily turns a 13x6, try a 12x6 or 13x5 to start with. Then adjust from there as needed.

To go to a 4-bladed prop, decrease an additional inch in either dimension. If your normal prop choice is, for example, a 11x6, you would begin with a 10x5 and work from there to find a 4-bladed prop that best fits your circumstances.

When should I use a 2-stroke engine vs a 4-stroke?

A 4-stroke gives you more torque, more power off the line, better vertical performance, and slower more scale flight speed because it turns larger diameter, lower pitch props. A 2-stroke is generally lighter and more powerful for the same displacement (not always) and goes faster, turning higher pitch lower diameter props.

Can you explain to me how a glow engine works? Is it just like a diesel truck engine?

Glow engines are a hybrid between diesel and gasoline engines in regards to their mode of operation. In a glow engine, the catalytic action of the platinum glow plug coil is what ignites the fuel-air charge rather than a spark or the heat due to compression of the mixture in the chamber. As a consequence, the compression ratio used tends to be higher than in a gasoline engine but lower than a diesel engine.

What is a 'pusher' prop or 'pusher' engine? What advantages are there to a pusher engine?

In a pusher installation the engine/prop are mounted on the back of the fuselage or the wing. This keeps the wake of the propeller unobstructed by the fuselage or other parts of the aeroplane - and is the primary advantage of the pusher configuration. A pusher propeller is twisted in the proper direction for airflow in a pusher installation.

I cannot get my engine far enough forward on the mount to reach the measurement called for in my plan's instructions. (For example, 5-3/4" from the firewall to the back of the spinner.) What can I do?

Some engines have very short case lengths and so cannot meet the measurements given. Simply use washers or plywood spacers to shim the motor mount away from the firewall until you can mount the engine properly to the mount and match the desired measurement.

How do I use after run oil?

We recommend application through the glow plug hole or through the air inlet. When SuperTigre states to not put after-run oil into the carb, they are referring to the fuel inlet. If you introduce the oil into the air inlet, you will have no problems.

When you use after-run oil, 2-5 drops are next to useless. You'll need to literally flood the engine with oil, so much so that the next time you start the engine, it will be difficult. We use at least a 1/2 teaspoon of oil, and sometimes more. A 3 oz. bottle of oil lasts about a dozen flying sessions.

If you are going to store your model and are worried about it dripping out, you might try a shower cap over the engine and also cotton plugs in the exhaust to avoid dripping. We also recommend a cotton cloth in the carb to minimize fuel leakage.

How should I set the airbleed and throttle stop screws on my glow engine?

Barrel stop screws are typically factory set between 1/16 to 1/8" open, which is about 1 mm. The air bleed screw is set so that the screw covers up half of the hole located on the side of the carb body.

My engine is overheating or running hotter than I would like. How can I get it better cooling?

Most people make the mistake of thinking more is better when it comes to the air INLET at the front of the cowl. This is a common error and while it seems logical the reverse is actually true.

To properly cool your engine you need more OUTLET not more inlet. You want at least 2:1, preferably 3:1 air out to air in otherwise it makes a 'dam' and the air can't come into the cowl because it has no where to go OUT of the cowl. If your engine is not cooling properly, try blocking off the other air inlet or opening the belly of the cowl further to better cool your engine. See the instruction manual for the Top Flite Corsair (pages 35, 40) for an example of making a baffle to properly cool your engine.

Important Engine Safety Precautions

No list is all inclusive, but here are some basics to watch for:

NOTE: Failure to follow these safety precautions may result in severe injury to yourself and others.
  • Keep all engine fuel in a safe place, away from high heat, sparks or flames, as fuel is very flammable. Do not smoke near the engine or fuel; and remember that the engine exhaust gives off a great deal of deadly carbon monoxide. Therefore do not run the engine in a closed room or garage.
  • Get help from an experienced pilot when learning to operate engines.
  • Use safety glasses when starting or running engines.
  • Do not run the engine in an area of loose gravel or sand; as the propeller may throw such material in your face or eyes.
  • Keep your face and body as well as all spectators away from the plane of rotation of the propeller as you start and run the engine.
  • Keep items such as these away from the prop: loose clothing, shirt sleeves, ties, scarfs, long hair or loose objects (pencils, screw drivers) that may fall out of shirt or jacket pockets into the prop.
  • Use a "chicken stick" device or electric starter; follow instructions supplied with the starter or stick. Make certain the glow plug clip or connector is secure so that it will not pop off or otherwise get into the running propeller.
  • Make all engine adjustments from behind the rotating propeller.
  • The engine gets hot! Do not touch it during or after operation. Make sure fuel lines are in good condition so fuel will not leak onto a hot engine causing a fire.
  • To stop the engine, cut off the fuel supply by closing off the fuel line or follow the engine manufacturer's recommendations. Do not use hands, fingers or any body part to try to stop the engine. Do not throw anything into the prop of a running engine.

How long can I store unopened fuel? how about opened fuel?
  1. Unopened fuel which is stored out of direct sunlight is literally good for years. We have opened 10-year old containers and had the fuel be fully potent and usable. However, in general it is a good idea to use the fuel off your shelves annually, especially if exposed to sunlight.
  2. Once fuel has been opened, it has been exposed to air which includes moisture. Both water and sunlight are your fuel's enemy, so the more frequently or the longer it is exposed the more rapidly it will deteriorate. In general we recommend customers use all open containers of fuel in a single modeling season then properly discard any remaining fuel.

My large two-stroke engine makes a "knocking" sound at medium to low throttle settings.

Large-bore engines, usually larger than .91 or so, tend to have a "knocking" or "clattering" sound when they are operated at less than full throttle. Many times, it sounds as if there is some kind of metal-to-metal contact going on inside the engine. Some modelers have suggested that one end of the connecting rod may have had too much clearance, which would cause the noise.

This has been extensively-investigated, and we've not been able to find any evidence of metal-to-metal contact that could cause such a noise. In fact, we've heard this sound from a wide variety of large engine sizes, and across several different brands. Engines that make the noise have been test run for considerable amounts of time and then disassembled so that all of the parts could be carefully examined.

No evidence of mechanical problems have ever been found. The noise comes from the exhaust system of the engine. Because model engines tend to run less smoothly at moderate throttle settings, the combustion process causes a resonance in the exhaust system that causes the clattering sound. It's not mechanical, just a result of the rapid expulsion of the exhaust gases when the engine's at less than full throttle.

It's nothing to be concerned about if the engine's running well.

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