Paraglider pilots moving to powered paragliding (PPG) tend to focus on the wing and the launch. The engine on their back gets treated like a scooter: fill up, pull the starter, fly. But a paramotor engine is a 2-stroke that runs at very high revs, is air-cooled and is lubricated by oil mixed into the fuel. It copes well when looked after properly and fails quickly when treated like a scooter engine. Every seizure in the air is a forced landing, and a good landing field is not always within reach.
This article is drawn from the PPG and paratrike training manual written by Mebayluon (10/2026), from its chapters on engines, fuel and maintenance. The worked examples are three common Vittorazi engines: the Atom 80 (foot-launch paramotor), the Moster 185 (single-seat trike, or foot-launch for heavier pilots) and the Cosmos 300 (two-seat trike). Figures come from Vittorazi's 2024–2025 manuals. Your engine may be a different version: every rev, temperature, torque and service-interval figure must be checked against the manual supplied with your engine. General equipment, launching and landing are covered in Paramotor (PPG) basics.
1. What kind of engine a paramotor uses
PPG engines span a very wide range: from about 80 cc on foot-launch units to 500 cc, and even 1,100 cc on large trikes. Most are 2-strokes, but there are 4-strokes too, such as the Rotax 912 and some larger aircraft engines adapted to PPG frames. This article covers 2-stroke engines only. Solo machines (foot-launch units and single-seat trikes) usually have a single cylinder. Trike engines, especially on two-seat tandem trikes, are mostly twin-cylinder, the exceptions being a few large single-cylinder trike engines such as the Vittorazi Cosmos 300 (used as an example below) or the Simonini Victor 1 (about 400 cc). A 2-stroke fires on every revolution rather than every other one like a 4-stroke, so it is very powerful for its weight, and also runs hotter. There is no separate oil pump: oil premixed in the fuel passes through the crankcase and lubricates the piston and crankshaft. Fuel without oil seizes the engine within minutes. In flight the engine usually runs at 3,000–10,000 rpm, far faster than a propeller more than a metre long can turn efficiently, so there is always a reduction drive (reducer) between them to slow the propeller down.
| Atom 80 | Moster 185 EFI | Cosmos 300 EFI | |
|---|---|---|---|
| Displacement | 78,2 cc | 185 cc | 293.9 cc, water-cooled |
| Power | 16 hp / 9,500 rpm | 25 hp / 7,800 rpm | 36 hp / 7,500 rpm |
| Engine weight | 10,4 kg | 14,3 kg | 25–27 kg (with radiator) |
| Fuel system | Walbro WB-37 diaphragm carburettor | Electronic fuel injection (EFI) | Electronic fuel injection (EFI) |
| Typically fitted to | Foot-launch paramotor, pilots up to ~85 kg | Single-seat trike, pilots 50–120 kg | Two-seat trike, tandem |
More power is not always better. Enough thrust makes inflation easy, the take-off run short and the climb quick. Too much makes the throttle twitchy and the torque (the reaction that turns the pilot opposite to the propeller) strong: according to the PPG Bible, once thrust exceeds roughly 70% of the pilot's weight, torque becomes harder and harder to control. Thrust also falls with altitude, to about 80% of its sea-level value at 1,500 m. Example: the Atom 80 gives about 52 kg of static thrust; for a 70 kg pilot that is already 74% of body weight, so throttle-up must be gradual.
2. Diaphragm and float carburettors, and electronic fuel injection
Carburetted 2-strokes use one of two types: the diaphragm carburettor and the float carburettor. The diaphragm type (Walbro, Tillotson, as on the Atom 80) has no float bowl, so it runs in any attitude and tolerates vibration; it is common on foot-launch engines. The fuel path through a diaphragm carburettor:
- In-tank fuel filter → primer bulb (squeeze to fill the line on a cold engine) → diaphragm pump, driven by crankcase pressure pulses through a small pulse line.
- The metering diaphragm and inlet needle keep the right amount of fuel in the carburettor: suction on the diaphragm pushes the lever and opens the needle; once full, the needle closes.
- The L screw sets the mixture at idle and low throttle, the H screw at high throttle. Screwing in (clockwise) leans the mixture; screwing out richens it.
- A loose or cracked pulse line means fuel starvation at high power. A dirty carburettor screen or in-tank filter makes the engine run lean and risks a seizure.
A float carburettor has a float bowl like a motorbike carburettor (Bing, Dell'Orto) and is common on trike engines and large-displacement engines. A float and needle valve hold the fuel level in the bowl: as the level drops the float drops and the needle opens; once full, the float pushes the needle shut. The mixture is set by jets and the needle rather than L/H screws, so richening or leaning means changing a jet or moving the needle clip. Points to remember with float carburettors:
- The carburettor must be mounted in the attitude the manufacturer specifies. Strong vibration makes the fuel in the bowl froth and the float bounce, so the engine alternates between rich and lean; this is why float carburettors are usually fitted on a rubber anti-vibration manifold.
- A float needle stuck open floods the engine, with fuel dripping from the bowl vent. A punctured or sticking float gives the wrong fuel level, so the engine runs abnormally lean or rich.
- Water and sediment collect in the float bowl, especially with ethanol fuel. Drain the bowl through its drain screw at the service intervals and before long storage.
The EFI versions (Moster 185 EFI, Cosmos 300 EFI) replace the carburettor with an electronic control unit (ECU), an electric fuel pump and an injector. The ECU works out the fuel quantity from revs and temperature, so there is no primer bulb and no L/H screws to adjust. A display shows revs, CHT, EGT, fuel used and warnings. According to Vittorazi, the Moster 185 EFI uses up to 30% less fuel, around 2.5 litres per hour at 30 kg of thrust. In exchange, everything runs on electricity from a 4-cell LiPo battery (14.8 V): a flat battery stops the engine.
- Charge the battery fully before every flying day (a full battery lasts about 7 flight hours) and watch the level on the display. For a full day of training, carry a charged spare.
- Charge only with the manufacturer's charger, supervised, on a non-flammable surface. Replace a battery that swells, dents or runs unusually hot. For long storage, keep it at storage voltage somewhere cool and dry.
- An EFI engine that won't start usually has a weak battery, a blown fuse (there are 15 A and 60 A fuses) or a loose connector; carry spare fuses. If the display shows a fault, land and look up the code in the manual; ECU software updates are a dealer job.
3. Mixing fuel and oil: ratios and what to buy in Vietnam
In Vietnam, PPG pilots most often use Liqui Moly 2T and Eni 2T oils. Motul 2T is used too, but less widely. Each brand makes several 2T lines, from mineral scooter oils to fully synthetic racing oils, so read the exact product name and the specifications printed on the can rather than just the word "2T":
| Oil | Base | Specifications | For a paramotor |
|---|---|---|---|
| Liqui Moly Motorbike 2T Synth Street Race | Fully synthetic | JASO FD, ISO-L-EGD, API TC | Recommended |
| Liqui Moly Motorbike 2T Offroad | Semi-synthetic | JASO FC, ISO-L-EGC, API TC | Stop-gap only |
| Liqui Moly Motorbike 2T Basic Scooter | Mineral | JASO FB, ISO-L-EGB, API TC | Do not use |
| Eni i-Ride racing 2T | Synthetic | JASO FC/FD, ISO-L-EGD | Recommended |
| Eni i-Ride moto 2T extreme tec | Fully synthetic | JASO FD, ISO-L-EGD | Recommended |
| Eni i-Ride 2T SML | Synthetic technology | JASO FC, API TC | Stop-gap only |
| Motul 710 2T | Fully synthetic (ester) | JASO FD, ISO-L-EGD, API TC | Vittorazi's reference oil |
- JASO FD and ISO-L-EGD are the top grades for premix 2-stroke oil: strong detergency, little carbon on the exhaust port, rings and plug, and little smoke. JASO FC is one step lower; JASO FB is old-style scooter oil. A paramotor runs at high load for long periods, so choose FD.
- Don't mix to the ratio printed on the can. Liqui Moly Synth Street Race says "mixing ratio up to 1:100": that is the oil maker's limit for motorbikes. A paramotor is mixed to the engine manual.
Vittorazi sets up its carburettors at the factory for Motul 710 2T at 2% (1:50), or Motul 800 2T at 1.5%. With another fully synthetic JASO FD oil (Liqui Moly, Eni), keep to 2% unless your engine manual says otherwise. Measure with a graduated cup, never by eye:
| Fuel | 2.0% (1:50): Liqui Moly, Eni, Motul 710 | 1.5%: Motul 800 only |
|---|---|---|
| 1 litre | 20 ml | 15 ml |
| 2 litres | 40 ml | 30 ml |
| 5 litres | 100 ml | 75 ml |
| 10 litres | 200 ml | 150 ml |
- Petrol: since 1 June 2026, Vietnamese filling stations only sell E10 and E5 ethanol blends. Choose E10 RON 95 (95-V or 95-III) and avoid E5 RON 92.
- Ethanol fuel absorbs water. Mix only what you will use in 1–2 days and keep it in a sealed can; drain the engine's tank if you stop flying for more than 2 weeks. Fuel lines and primer bulbs also age faster with ethanol, so inspect them more often.
- Oil: pick one fully synthetic JASO FD oil and stick with it; never mix two brands in one tank. Never use 4-stroke motorbike oil, mineral 2T scooter oil or TC-W3 outboard oil.
4. Pre-flight engine checks and warm-up
The recommended sequence has five steps, based on Vittorazi's and the frame manufacturers' manuals:
- Cold, not running: propeller (cracks, chips, bolts, safety wire), frame and engine mounts, exhaust with its springs and safety ties, fuel lines, filter and tank vent, spark plug and cap, throttle cable returning fully, kill switch, belt and gearbox. EFI engines: battery full, fuses, no fault on the display. Cosmos 300: coolant.
- Starting: nobody within about 6 m of the propeller plane, shout "CLEAR PROP", throttle at idle. Atom 80: squeeze the primer if cold; EFI: switch on the ECU and wait for the pump to fill the line. Hold the motor firmly, or chock the trike's wheels.
- Warm-up: light throttle for about 30 seconds so the oil spreads, then hold mid revs until the manufacturer's temperature is reached. Listen to the engine and look for fuel leaks or odd vibration.
- Full-power test, 15–20 seconds: maximum revs within the manufacturer's range, no hesitation on throttle-up, a stable idle afterwards, kill switch tested.
- Just before take-off: CHT and EGT in range; enough fuel for the flight plus reserve; throttle cable free; trimmers at the take-off setting.
How long to warm up
For the Atom 80, Vittorazi's manual says: after 30 seconds of light throttle, hold about 6,000 rpm until CHT reaches about 70 °C, then do the full-power test. Real time depends on the weather: above 15 °C it usually takes 2–3 minutes, below 15 °C 5–6 minutes. Winter mornings in Sa Pa and Ha Giang can drop below 5 °C; then run longer and watch the CHT gauge, not your watch. The Moster 185 EFI warms up to about 80 °C CHT; the water-cooled Cosmos 300 waits for coolant to reach its working range. Never go to full power on an engine that isn't warm.
Never prime a hot engine. If it won't fire after a few pulls, suspect flooding: remove the plug, dry it, pull a few times at full throttle to clear the excess fuel, refit and start. EFI engines start differently: throttle at idle whether cold or hot, press the start button twice and hold until it fires; if revs exceed 3,500 rpm in the first 4 seconds, the ECU shuts the engine down as a safety measure.
5. Rev and temperature limits: EGT and CHT
The two most important gauges on the engine are EGT (exhaust gas temperature) and CHT (cylinder head temperature). They measure different things:
- EGT is read by a thermocouple probe in the exhaust header, close to the port, in the hole the manufacturer provides. It reacts within seconds, so it shows the mixture as soon as you change throttle. EGT rises with revs; a lean mixture sends EGT shooting up. The Atom 80 limit is 650 °C.
- CHT is read by a thermocouple ring under the spark plug, or by a sensor in a dedicated hole in the cylinder head (2025 versions). It reacts slowly and shows overall heat load and cooling: use it to know when the engine is warm enough to fly, and to catch prolonged overheating.
- Limits only apply to the manufacturer's sensor position. The Atom 80 has two CHT limits: 180 °C with the under-plug ring, 120 °C with the dedicated sensor, so know which one your engine has. Route sensor wires away from the exhaust and propeller; clamp the EGT probe tightly, because if it drops into the propeller the propeller is finished.
| Atom 80 | Moster 185 EFI | Cosmos 300 EFI | |
|---|---|---|---|
| Idle | 1,800–2,000 rpm | 2,000–2,200 rpm | 1,800–2,000 rpm |
| Maximum rpm | 9,600–9,800 rpm | 8,400–8,700 rpm | 7,300–7,650 rpm |
| Cruise, long climbs | ≤ 8,000 rpm (level flight ~7,000) | ≤ 7,000 rpm | ≤ 6,500 rpm |
| Continuous full power | under 30 seconds | under 30 seconds | under 30 seconds |
| Maximum temperature | CHT 180 °C (under plug) or 120 °C (dedicated sensor); EGT 650 °C | CHT 208 °C (on the display) | Coolant 65–90 °C |
| Warm up to | CHT ~70 °C | CHT ~80 °C | Coolant in working range |
Can you hold full power continuously? No. Full power is for take-off and short climbs only, under 30 seconds. For a long climb, throttle back below the engine's cruise limit. New pilots often hold full power all the way up for fear of being low; it is the quickest way to hole a piston.
6. Lean and rich mixtures: how to recognise and adjust
| Lean (too much air) | Rich (too little air) | |
|---|---|---|
| Running | Revs shoot up, engine "screams"; hesitates on quick throttle-up; may die when throttling back | Sluggish, smoky, won't reach maximum revs, burbles |
| Temperatures | CHT and EGT abnormally high | CHT and EGT low |
| Spark plug | White or pale grey, possibly with metal specks | Black, oily and wet |
| Usual causes | H screw too far in; dirty filter; air leak (gasket, seal); hardened diaphragm; tuned on a hot day then flown on a cold one | Screw too far out; air filter or intake blocked; inlet needle not sealing; over-priming |
| Consequence | Overheating, seizure, holed piston | Carbon build-up, fouled plug, low power |
A correctly tuned Atom 80 idles steadily, picks up instantly, runs smoothly at cruise revs and reaches maximum revs within the manufacturer's range. The rule: slightly rich is better than lean. Rich only makes the engine dirty and weak; lean kills it. Adjust from the manufacturer's base setting, with the engine warm, no more than 1/8 of a turn at a time, and only if you have been shown how. EFI engines have no screws: the ECU manages the mixture, and pump parameters are only changed with the engine warm, exactly as the manual says.
7. Common faults and what to do
| Fault | Signs | Usual causes | Fix and prevention |
|---|---|---|---|
| Seizure, scuffed piston | Sudden rev drop, engine stops, knocking; may restart once cool | Lean mixture, too little oil, overheating, too long at full power, no warm-up | Throttle back and land; don't restart to keep flying; strip and inspect piston and cylinder |
| Holed or melted piston crown | Loss of compression, weak or won't start; aluminium specks on the plug | Lean mixture, wrong plug, poor fuel causing detonation | Replace the piston; find and fix the root cause before flying again |
| Sticking inlet needle | Stuck shut: no fuel, dies on throttle-up. Stuck open: flooding, fuel dripping from the carburettor | Dirt, old fuel gumming up; debris on the seat, spring, or lever at the wrong height | Clean, replace needle and diaphragm kit; clean fuel filter; check lever height |
| Pulse line or pump diaphragm failure | Fuel starvation at high power | Cracked pulse line, hardened diaphragm | Replace the line, fit a carburettor rebuild kit |
| Air starvation | Won't rev, runs rich, smoky | Intake covered (bag, jacket), dirty air filter, high field, hot day | Check the intake, clean the filter, adjust for conditions |
| Oil or fuel weeping around the crankcase | Oil or fuel seeping; engine gradually runs leaner | Aged crankcase seals or gaskets | Dangerous: the air leak leans the engine; fix before flying |
| Fouled or worn spark plug | Hard starting, misfiring | Rich mixture, long idling, over 25 hours | Fit a new NGK BR9ES gapped correctly |
Seizure in flight: throttle back at once, fly it as a paraglider and pick a landing field. After one seizure the engine must be stripped and inspected, not "tried again to see". A cooled engine will often restart, and that is the trap: a scored piston will seize again, perhaps where there is nowhere to land.
Engine won't start: work through the four essentials, spark, fuel, air, compression, starting with the cheapest and easiest: the plug. If flooded, dry the plug as above. No fuel? Check the filter, kinked lines and the tank vent. A broken starter cord, loose bolts or a lost exhaust spring can be fixed on the field if you carry the right kit.
8. Operating habits that make an engine last
- Change throttle smoothly, and avoid holding one fixed rpm for too long.
- Long descents at idle cool the engine and foul the plug: blip the throttle from time to time.
- Shutting down: after hard running, idle for about a minute to let temperatures settle, then press the kill switch.
- Cooling: the Atom 80 and Moster are air-cooled and overheat easily during long ground runs with no airflow. On the Cosmos 300, check coolant, radiator and fan.
- Listen to the engine: knocking, odd vibration or dropping revs mean throttle back and head for the field or land. Don't carry on "to finish the flight".
- Don't use a throttle lock (cruise control). It is a leading cause of propeller accidents. The kill switch must be reachable by the hand holding the throttle.
9. Maintenance by engine hours
Every engine should have a logbook and an hour meter. Fill it in straight after each session: engine hours, revs, temperatures, dates of plug and fuel-line changes, bolt checks, odd noises, incidents. A problem found between intervals gets fixed at once, not at the next interval. The schedule below follows Vittorazi's 2025 maintenance manuals:
| Interval | Main items |
|---|---|
| Every flight | 5-step pre-flight check; wipe the engine down; log hours, revs and temperatures |
| 10 hours | Check torque on cylinder-head, exhaust, mount and propeller bolts; exhaust springs and safety wire; clean the decompression port (every 10–20 hours) |
| 25 hours | Replace the NGK BR9ES plug (0.7 mm gap new, replace beyond 0.9 mm); clean the fuel filter and carburettor screen |
| 50 hours | Inspect piston, rings, cylinder and head (carbon, scoring); Cosmos 300: bearings too |
| 100 hours | Replace the ring set; replace the plug cap (Moster 185); Cosmos 300: coolant, hoses, radiator |
| 150 hours | Replace the piston (with rings and gudgeon pin) |
| 200 hours | Full workshop inspection per the manual: crankshaft bearings, seals, clutch, gearbox |
| By age | Replace fuel lines at least every 2 years and don't clamp them with ordinary cable ties; premix left open can go off in about a week |
- Reduction drive and clutch: gearbox properly greased or oiled, bearings in good shape. Propeller play with tight bolts points to a bearing. A healthy clutch means the propeller stands still at idle and spins freely with the engine off. A propeller turning at idle suggests a broken clutch spring. Any odd noise from the reduction drive gets dealt with at once.
- Cylinder-head bolts are re-checked with a torque wrench within 10 hours of any replacement. After tightening, add a paint mark so a loose bolt is visible at a glance. Exhaust springs always carry safety wire (the thickest size, never reused) so a spring that pops off cannot reach the propeller.
10. The propeller: the biggest risk in the sport
According to the PPG Bible, the propeller is the number one cause of serious injury in powered paragliding, and most of it happens during start-up, not in flight. The cage protects the propeller and the lines, not people. The book's reminder: whatever can reach the propeller eventually will.
- The inner hoop of the cage is about 2.5 cm smaller than the propeller diameter so a hand cannot get in. The fuel tank sits at least 15 cm from the blade tips: the biggest fire risk is the propeller cutting into the tank in a fall.
- Nothing loose: no scarves, tuck away spare harness straps and helmet cords. Propellers should break easily on impact (wood, light carbon).
- Fitting a propeller: the curved face points in the direction of flight. The propeller is held by friction and loose bolts will shear; never drill extra holes. Use grade 8.8 or 10.9 bolts with at least 2 threads showing. Tighten in a cross pattern: finger-tight in order 1 → 6, then build up torque in the same order to the manufacturer's value.
- Balancing and repair: mount it on a balancer through the centre hole; the side that drops is heavy, so add weight to the light side as the manufacturer directs. Up to 6 mm of track difference is acceptable if there is no vibration. Small dings in wood can be filled with glue and baking soda, fully cured, sanded and rebalanced. Damage near the hub is more dangerous; carbon damage longer than 7.5 cm goes to a professional. If in doubt, replace it.
11. What you can do yourself, and what goes to the workshop
| Pilot can do | Send to the manufacturer or a certified technician |
|---|---|
| Pre-flight checks, cleaning, storage | Opening the engine or gearbox; deep carburettor work; ECU work |
| Assembly and disassembly for transport | Carbon propeller repairs, damage near the hub |
| Replacing the plug, fuel lines, starter cord | Wing inspection (porosity, line strength, trim) |
| Tightening bolts, safety-wiring, paint marks | Reserve repacking |
| Mixing fuel, keeping the logbook | Line replacement, riser or load-bearing harness repairs |
A PPG pilot's reserve has its own schedule: wet gear means a repack, and the handle sits near the hip, never pulled with the throttle hand. Details in Paraglider and paramotor reserves: packing, installation, tips.
12. The field toolkit
The goal: be able to tighten anything loose, change the plug, replace a belt and adjust the carburettor right on the field.
- Tools: 3, 4, 5 and 6 mm hex keys; 3–8 mm sockets and a plug socket; carburettor adjusting screwdriver; locking pliers; knife.
- Spares: spare plug; fuel line; cable ties; about 60 cm of safety wire; quick-set glue; ripstop repair tape; spare fuses (EFI engines).
- For cross-country: a bottle of 2-stroke oil for one tank; a fully charged phone; hook knife; first-aid kit; small fire extinguisher.
The engine is only half of the flying machine. The other half is the wing and how you hang beneath it: see Paramotor hang check: how to balance your hang points and What is a reflex wing? How to use it and when it gets dangerous. If you would like to try a powered paragliding flight and see these engines at work, come to Mebayluon's Khau Pha flying site.