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Your initial 2-stroke: a simple guide

Two-stroke feverishness engines are by distant a many renouned engines used to energy RC indication airplanes. They are comparatively inexpensive for a energy they produce, they are easy to start, run and maintain, and once we learn how to scrupulously take caring of them they will final for many years. Let’s take a closer look.


Starting during a tip of a engine is a cylinder head. It is bolted into place and has a threaded hole in a core for a feverishness plug.

The area between a bottom aspect of a cylinder conduct and a tip of a piston is a explosion chamber. The bottom of a feverishness block and a gold component can also be seen here.

All indication kits and ARFs have a endorsed engine distance range. Typically this will be something like .25 to .32, or .40 to .60, etc. You should select an engine that is within this range, and for improved stand opening we should collect an engine closer to a aloft side of a range. When it comes to selecting a propeller for your engine, we should also follow a recommendations found in a engine’s operation guide.


If we have never owned or run a 2-stroke engine afterwards some of a vernacular needs to be explained. Here’s a glossary of 2-stroke engine terms:

ABC– refers to a materials that make adult a engine’s piston and sleeve; an aluminum piston (A), propitious into a coronet sleeve (B), that has been chrome plated (C). An AAC engine is one with an aluminum engine propitious into an aluminum sleeve that has been chrome plated.

Case -the engine’s categorical body. Most are expel in one or dual tools from aluminum, yet some specialty engines are done from fully-machined aluminum stock.

Connecting rod -also referred to as a “conrod,” this is a partial of a engine that connects a piston to a crankshaft. The conrod has bushings during any finish and is connected to a piston with a wrist pin (top end), and is connected to a crankshaft with a holder pin (bottom end).

Cylinder head- the tip partial of a engine customarily bolted into place with possibly 4 or 6 bolts or screws. A threaded hole in a core is where a feverishness block is installed. The underside of a cylinder conduct is machined to form a tip of a explosion chamber.

Ports– openings and channels machined into a sleeve and engine box that concede a send of a air/fuel reduction from a engine box into a explosion cover and, after combustion, out by a exhaust.

Sleeve– a cylinder’s inner subsidy or ìliner.î A tubular, coronet structure that houses and guides a piston, a sleeve has a prosaic edge prong that fits between a engine box and cylinder conduct to reason it in place. Port openings are machined in a side of a sleeves that align with a send channels in a engine case.


The partial of a engine that a piston fits into and is guided by is a sleeve. Made of brass, it has openings (ports) machined into it to concede a upsurge of fuel mixture.

The crankshaft translates a adult and down suit of a piston into series force to spin a propeller. The opening in a core of a crankshaft is a intake port. It aligns with a carburetor’s venturi and allows a atmosphere and fuel reduction to enter a engine box by a holes in a behind of a holder web.


With many engines, a box customarily has 3 parts: a front housing that houses a crankshaft and categorical bearings, a crankcase that is a categorical box that a cylinder is trustworthy to, and a behind image that seals a behind of a engine. It is customarily reason in place with 4 bolts or screws and can be hermetic with possibly a skinny gasket or an inner O-ring.

The crankcase is upheld in a front housing with a vast behind temperament and a smaller front bearing. In reduction costly engines, plain bronze bushings can be used in place of a round bearings. A column bulb and a bearing washer reason a column firmly to a front finish of a crankshaft and during a behind is a vast counter-weighted web and crankpin used to bond a crankshaft to a conrod. The conrod is trustworthy to a piston with a wrist pin and a piston fits within a sleeve, that fits into and is upheld by a cylinder partial of a engine case. The conduct fits on tip of a sleeve and a space between a tip of a piston and a bottom of a conduct forms a explosion chamber.

Depending on a pattern of a engine, a piston can be hermetic with possibly a piston ring that fits between a piston and a sleeve, or a piston can be hermetic with a slight finish (smaller during a top) in a sleeve. This is how an ABC engine is set up.


The piston is connected to a joining rod with a wrist pin. A open handle shave binds a wrist pin within a piston body.


The engine’s energy is tranquil by a carburetor. The carburetor is done adult of a categorical body, a stifle barrel, a high-end and low-end needle valve assembly, a mist bar and a venturi. Air enters a carburetor by a venturi opening and a volume of atmosphere is tranquil by a rotating stifle barrel. A stifle arm is trustworthy to a tub so it can be rotated open and sealed by a stifle linkage and servo.

The fuel enters a venturi by a high-end (main) needle valve and it sprays into a try by a hole in a side of a mist bar. By branch a categorical needle valve in (clockwise) we gaunt out a fuel atmosphere reduction by alleviation a volume of fuel relations to a air. By branch it counterclockwise we richen a reduction by vouchsafing some-more fuel upsurge in. The low-end (idle) needle valve is customarily located during a core of a carburetor’s stifle arm and it adjusts a reduction while a engine is doing during idle to about º throttle.

It might need a skinny screwdriver to adjust.


The feverishness block lights adult when we vitalise it with a feverishness motorist battery. It ignites a fuel reduction in a explosion chamber.

The feverishness plug
is used to light a fuel reduction within a explosion chamber. The feverishness block has a 1/4-28 thread and it screws into place in a hole in a core of a engine head. In a core of a feverishness block is a coiled component done of gold wire. The feverishness block is initial energized with a 1.2V feverishness motorist battery, and afterwards a application of a fuel reduction and a feverishness generated by that application causes a feverishness block to light a fuel charge, most like how a diesel lorry engine operates. Once a engine is started and warms adult for a tiny while, mislay a feverishness motorist battery and a engine will continue to run. Catalytic movement between a methanol fuel and a gold in a feverishness block component as good as a engine feverishness keep a component intense once it has been illuminated with a starting battery.


A 2-stroke engine creates one series for any energy cycle. As a piston moves ceiling in a sleeve, it compresses a uninformed assign of fuel/air mixture. The application heats adult a fuel reduction and is lighted by a feverishness plug. As a piston travels ceiling it also creates a disastrous vigour section in a crankcase next a piston. This draws atmosphere and fuel into a crankcase from a carburetor and into a intake port. The intake pier is machined in a side of a crankshaft and it lines adult with a carburetor’s venturi and it opens adult to a vale core of a crankshaft. The atmosphere and fuel transport by a vale crankshaft to enter a crankcase.

As a piston travels downward after a fuel reduction is combusted, a criminal rod turns a crankshaft and this closes a intake port. The piston continues downward and starts to restrict a new assign of fuel mixture. When a piston passes a bypass pier this opens a pier to concede a dense reduction to upsurge adult a send channel between a engine box and a sleeve. This happens only as a spent fuel reduction assign exits a dull port. The piston goes behind adult and closes a dull pier and starts to restrict a new fuel reduction assign so opening a intake pier so another new fuel reduction assign can enter a engine and start a cycle all over again. A finish energy cycle requires 2-strokes of a piston in a sleeve.



By stealing a engine’s behind image we can see a piston’s conrod trustworthy to a tiny crankpin during a behind of a crankshaft.

Don’t only shaft a code new engine into a aeroplane and go flying. To furnish limit power, a fresh-out-of-the-box engine needs some special handling. The piston and a sleeve need to be gradually propitious together for a accurate fit. This procession is famous as “breaking in.” If we don’t take a time to break-in your engine, extreme feverishness built adult from attrition can means inner repairs and a piston and sleeve will never sign properly.

First, implement a new feverishness block (the correct length and form is indicated in your engine’s instruction manual), tie it with your fingers afterwards tie it down about ? spin with a feverishness block wrench. Connect a fuel lines to a carburetor and fill a tank with uninformed feverishness fuel. Use fuel with a same nitro calm (typically 10 to 15 percent) that we devise to run a engine with and be certain your fuel contains during slightest 18 percent lubricating oil. Install a endorsed column and column washer afterwards tie a column bulb with a 6-inch tractable wrench. Close a categorical needle valve totally by branch it clockwise, and afterwards open it about 4 full turns counterclockwise. Open a stifle entirely afterwards primary a engine by fixation your ride over a carburetor opening and flipping a column several times. Continue until we see fuel upsurge by a fuel line and into a carburetor.

Close a stifle to about 1/4, insert a feverishness motorist battery to a feverishness block and use an electric starter to spin a engine over. Don’t use your fingers; if we don’t have an electric starter afterwards use a “chicken stick” accessible from a hobby shop. Once a engine starts, let it comfortable adult a tiny afterwards open a stifle entirely and let it run with a really abounding needle environment for about 5 to 7 minutes, and afterwards close a engine down and let it cold off for 10 to 15 minutes. Repeat this routine several times while gradually disposition out a needle-valve reduction a few clicks any time. Don’t run your engine during full stifle with a gaunt environment until you’ve run during slightest 6 to 8 tanks of fuel by a engine.

A scrupulously broken-in engine will run consistently but overheating and will transition uniformly from idle to full power. Try to equivocate a enticement of disposition your engine to get any final unit of power. This leads to overheating. It is always improved to adjust your indication for rise rpm (using a good digital tachometer), and afterwards subsidy down a categorical needle to richen a reduction until we mislay about 200rpm.


Basic support equipment: Nitro fuel and fuel pump, electric starter, feverishness motorist batteries, a digital tachometer, hint feverishness plug, glow-plug wrench, assorted round drivers and screwdrivers. An additional column or dual also come in handy. A SlimLine Nitro Power Station is also shown.


It is also really important
to adjust your engine’s low-end (idle) needle valve so your engine will work uniformly and consistently while during idle. A scrupulously set low-end needle valve allows a engine to transition uniformly from idle adult to full power. If a engine hesitates and dies when we open a throttle, a low finish is too lean. If a engine burbles, coughs and has a severe transition, a low-end needle is too rich. Make your adjustments by ? turns during a time until your engine operates uniformly and consistently.


Here’s a list of things to do to keep your engine happy:

  • ï Use fresh, purify fuel.
  • ï Install a fuel filter in your engine’s fuel complement and in your fuel container.
  • ï At a finish of a day, dull your fuel tank and run a final bit of fuel out of a tank by starting and using a engine.
  • ï Never leave fuel in a tank for extended periods.
  • ï Use an after-run oil after a final moody of a day and before we store your engine for an extended duration of time. Add a few drops down a carburetor and mislay a feverishness block so we can supplement a few drops into a piston and sleeve assembly.
  • ï Always change your propellers and easily silt a heading and trailing edges to mislay any pointy flashing.
  • ï Never use a nicked or shop-worn propeller.
  • ï If all of a remarkable your engine won’t start adult readily, reinstate a feverishness plug.

Flying indication airplanes powered with 2-stroke feverishness engines is sparkling and really satisfying. Once we learn how to work and scrupulously say these considerable tiny powerplants they’ll continue to acquire their keep for many years to come. They are a really good investment and can be used to energy several opposite planes.

For minute information on 2-stroke feverishness engines, see Dave Gierke’s glorious books: “2-Stroke Glow Engines for R/C Aircraft, Vol. 1” and “2-stroke Glow Engines Vol. 2: Power Beyond a Basics,” accessible from


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