The 2si 690 is a family of in-line three cylinder, liquid-cooled, two-stroke, dual ignition, aircraft engines that were designed for ultralight aircraft.
The basic engine was originally designed and produced by JLO of Germany and was later acquired by the AMW Cuyuna Engine Company of Beaufort, South Carolina and marketed under the Cuyuna brand name. Later the engine was marketed by Cuyuna under the Two Stroke International (2si) brand. Cuyuna no longer markets engines for aircraft use although the 690 was still in production as an industrial and marine engine.
The 690 is a conventional three-cylinder engine that weighs 89 lb (40 kg) in its L70 aircraft and marine versions. The aircraft engine features dual capacitor discharge ignition (single in the marine and industrial versions), reed valve porting, tuned exhaust system, three slide venturi-type carburetors, liquid cooling, fuel pumps, a cast iron cylinder liner, ball, needle and roller bearings throughout. The aircraft version was offered with an optional gearbox reduction dive system and a centrifugal clutch. The current industrial and marine version has an available gearbox with ratios of 2.04, 2.65 or 3.06:1. Starting is electric start only.

Variants:

690-L70 aircraft engine
Gasoline aircraft engine with triple carburetors, 70 hp (52 kW) at 6250 rpm, weight 89 lb (40 kg), out of production.

690L-70 industrial and marine engine
Gasoline industrial and marine engine, triple carburetors, 70 hp (52 kW) at 6250 rpm, weight 89 lb (40 kg), electric starter mounted on the accessory cover end.

690AL-70 industrial and marine engine
Gasoline industrial and marine engine, triple carburetors, 70 hp (52 kW) at 6250 rpm, weight 89 lb (40 kg), electric starter mounted on the power take-off end.

Specifications:

690-L70 aircraft engine
Type: Three-cylinder, two-stroke aircraft engine
Bore: 69.5 mm (2.74 in)
Stroke: 60 mm (2.36 in)
Displacement: 684 cc (41.7 cu in)
Length: 21.6 in (549 mm)
Width: 19.05 in (484 mm)
Height: 13.9 in (353 mm)
Dry weight: 89 lb (40 kg)
Valvetrain: reed valve porting
Ignition: Electronic
Fuel type: Minimum 92 octane
Oil system: premixed oil and fuel at 50:1
Cooling system: liquid cooled
Reduction gear: optional gearbox
Reduction: Mechanical Integral damper
Reduction Ratio: 2.04-1 to 3.06-1
Power output: 70 hp (52 kW) at 6250 rpm
Fuel consumption: 5.1 US gal/h (19.3 l/h) at 75% power
Max torque: 94 at 5250
Price 1998: US$2975

The 2si 540 and 2si 500 are a family of in-line twin-cylinder, liquid-cooled, two-stroke, dual ignition, aircraft engines that were designed for ultralight aircraft.
The basic engine was originally designed and produced by JLO of Germany and was later acquired by the AMW Cuyuna Engine Company of Beaufort, South Carolina and marketed under the Cuyuna brand name. Later the engine was marketed by Cuyuna under the Two Stroke International (2si) brand. Cuyuna no longer markets engines for aircraft use although the 540 was still in production as a sport vehicle engine.
The 540 is a conventional twin-cylinder engine that weighs 90 lb (41 kg) in its L70 aircraft version. The engine features dual capacitor discharge ignition (single in the sport vehicle version), reed valve porting, tuned exhaust system, two slide venturi-type carburetors, liquid cooling, fuel pump, a cast iron cylinder liner, ball, needle and roller bearings throughout. The aircraft version was offered with an optional gearbox reduction system. Starting is electric starter or recoil starter.
The 500L85 is a special engine that was developed from the 540, by reducing the cylinder bore from 75 mm (2.953 in) to 72 mm (2.835 in). This was done to reduce the displacement to under 500 cc and allow the engine to be used for Formula 500 auto racing.

Variants:

500L-85
Gasoline sport vehicle engine for Formula 500 auto racing. Dual carburetors, 83 hp (62 kW) at 8000 rpm.

540-L70
Gasoline aircraft engine, dual carburetors, 70 hp (52 kW) at 7000 rpm, weight 90 lb (41 kg), out of production.

540L-90
Gasoline sport vehicle engine for auto racing, kart and all-terrain vehicle applications. Dual carburetors, 89 hp (66 kW) at 8000 rpm.

Specifications:

540-L70
Type: Twin-cylinder, two-stroke aircraft engine
Bore: 75 mm (2.95 in)
Stroke: 61 mm (2.40 in)
Displacement: 540 cc (32.95 cu in)
Length: 17.5 in (444.50 mm)
Width: 14.0 in (355.60 mm)
Height: 15.0 in (381.00 mm)
Dry weight: 90 lb (41 kg)
Valvetrain: reed valve porting
Ignition: Electronic
Fuel type: Minimum 92 octane
Oil system: premixed oil and fuel
Cooling system: liquid cooled
Reduction gear: optional gearbox
Reduction: Mechanical Integral damper
Reduction Ratio: 1.66-1 to 3.00-1
Power output: 70 hp (52 kW) at 7000 rpm
Max torque: 71 at 7000 rpm
Price 1998: 29,950 Fttc

The 2si 460 is a family of in-line twin-cylinder, two-stroke, single ignition, aircraft engines that were designed for ultralight aircraft.

The basic engine was originally designed and produced by JLO of Germany and was later acquired by the AMW Cuyuna Engine Company of Beaufort, South Carolina and marketed under the Cuyuna brand name. Later the engine was marketed by Cuyuna under the Two Stroke International (2si) brand. Cuyuna no longer markets engines for aircraft use although the 460 is still in production as a diesel/multifuel or gasoline industrial, marine and sport vehicle engine.

The 460 is a conventional twin-cylinder engine that weighs 59 lb (27 kg) in its F35 aircraft version. The engine features single capacitor discharge ignition, piston porting, tuned exhaust system, one or two slide venturi-type carburetors, fuel pump, a cast iron cylinder liner, ball, needle and roller bearings throughout. The aircraft version was offered with cog belt drive or a gearbox reduction system. Starting is electric starter or recoil starter.

Variants

460-F35
Gasoline aircraft engine, single carburetor, 35 hp (26 kW) at 6000 rpm, weight 59 lb (27 kg), out of production.

460-F40
Gasoline aircraft engine, single carburetor, 40 hp (30 kW) at 6500 rpm, weight 70 lb (32 kg), out of production.

460-F45
Gasoline aircraft engine, dual carburetors, 45 hp (34 kW) at 6750 rpm, weight 70 lb (32 kg), out of production.

460 MF
Diesel/multi-fuel engine for marine and industrial applications, 37 hp (28 kW) at 6000 rpm, weight 78.5 lb (36 kg) without gearbox.

460F-35
Gasoline industrial engine and sport vehicle engine for auto racing, kart and All-terrain vehicle applications, single carburetor, 35 hp (26 kW) at 6000 rpm, basic weight 55 lb (25 kg).

460FE-35
Gasoline industrial engine and sport vehicle engine for auto racing, kart and ATV applications with electric start, single carburetor, 35 hp (26 kW) at 6000 rpm, basic weight 55 lb (25 kg).

460L-50
Gasoline marine engine powering a jet pump, 50 hp (37 kW) at 6750 rpm.

Specifications

460-F35 aircraft engine
Type: Twin-cylinder, two-stroke aircraft engine
Valvetrain: piston porting
Fuel type: Minimum 92 octane
Oil system: premixed oil and fuel
Cooling system: fan cooled
Reduction gear: cog belt or optional gearbox
Bore: 69.5 mm (2.74 in)
Stroke: 60.0 mm (2.36 in)
Displacement: 455 cc (27.77 cu in)
Length: 14.5 in (368.30 mm)
Width: 16.0 in (406.40 mm)
Height: 16.0 in (406.40 mm)
Dry weight: 59 lb (27 kg)
Power output: 35 hp (26 kW) at 6000 rpm

While developing the Pterodactyl Pfledge flying wing ultralight in the late 1970s, designer Jack McCornack experimented with a number of possible engines. Early flights used a German-made Sachs engine, but the high exchange rate and long lead times for this engine convinced him to try other options.

2si Cuyuna 340 / 430 / UL-II Article

McCornack settled on a two-stroke snowmobile engine produced by the Cuyuna Development Company as having the best potential. In 1979 He modified the engine with a crankcase extension, an additional main bearing, lowered the compression ratio using an additional head gasket and substituted a smaller 32 mm (1.26 in) Mikuni carburettor, amongst other modifications. The original snowmobile engine produced 40 hp (30 kW). Lowering the compression ratio not only de-rated the engine, but also made pull-starting easier and allowed it to run on lower-octane regular auto fuel. The resulting engine worked well, was de-rated to produce 30 hp (22 kW) at 5,500 rpm and proved reliable in service.
Citing liability concerns over producing a two-stroke engine for human-carrying aircraft applications, Cuyuna declined to produce the modified engine. Instead, Cuyuna decided that the resulting engine was different enough from the base snowmobile engine that they would supply assembled and test-run shortblocks as parts to McCornack’s company, Pterodactyl Limited, who would then complete the engines and be the manufacturer, allowing Cuyuna to continue producing snowmobile engines.
After two years of poor sales of snowmobiles, due to a dearth of snow and no lawsuits against Pterodactyl Limited regarding the engine, Cuyuna agreed to build the engines themselves.
The 430 was also produced in a reduced 2.362 in (60.0 mm) bore version called the 340. The modification reduced its displacement to 339 cc and output to 25 hp (19 kW) at 5500 rpm. The standard 430 has a bore of 2.658 in (67.5 mm).
Unit cost 1980: US$800

Variants
340D – Direct drive version, 25 hp (19 kW) at 5500 rpm, recoil starter.

340R – Reduction drive version using a belt drive system, 25 hp (19 kW) at 5500 rpm, recoil starter

430D – Direct drive version, 30 hp (22 kW) at 5500 rpm, recoil starter.

430F – Reduction drive version using a 3:1 gearbox system, dual carburetors, producing 45 hp (34 kW).

430R – Reduction drive version using a belt drive system, 30 hp (22 kW) at 5500 rpm, recoil starter

UL II – 35 hp (26 kW) version

Specifications

430D
Type: Direct drive two-stroke piston aircraft engine
Bore: 2.658 in (68 mm)
Stroke: 2.362 in (60 mm)
Displacement: 428 cc (26.11 cubic inches)
Dry weight: 65 lb (29 kg)
Designer: McCornack/Cuyuna
Fuel type: Regular auto fuel
Oil system: 40:1 premixed fuel and oil
Cooling system: fan forced air
Power output: 30 hp (22 kW)
Compression ratio: 12.5:1
Power-to-weight ratio: 0.46 hp/lb (0.76 kW/kg)

The basic engine was originally designed and produced by JLO of Germany and was later acquired by the AMW Cuyuna Engine Company of Beaufort, South Carolina and marketed under the Cuyuna brand name. Later the engine was marketed by Cuyuna under the Two Stroke International (2si) brand. Cuyuna no longer markets engines for aircraft use although the 230 was still in production as a diesel/multifuel or gasoline industrial and marine engine.
The 230 is a conventional single-cylinder two-stroke engine that weighs only 36 lb (16 kg) in its A20 version. The engine features single capacitor discharge ignition, piston porting, tuned exhaust system, slide venturi-type carburettor, fuel pump, a cast iron cylinder liner, ball, needle and roller bearings throughout. The engine was offered with cog belt drive or a gearbox reduction system. Starting is electric starter or recoil starter.

Variants

230-A20 – Gasoline aircraft engine, 20 hp (15 kW) at 6000 rpm, weight 36 lb (16 kg), out of production.

230-F22 – Gasoline aircraft engine, 22 hp (16 kW) at 6500 rpm, weight 48 lb (22 kg), out of production.

Specifications

230-A20
Type: Single-cylinder, two-stroke aircraft engine
Bore: 69.5 mm (2.74 in)
Stroke: 60.0 mm (2.36 in)
Displacement: 228 cc (13.91 cu in)
Length: 11.7 in (297.18 mm)
Width: 14.6 in (370.84 mm)
Height: 14.0 in (355.60 mm)
Dry weight: 36 lb (16 kg)
Valvetrain: piston porting
Fuel type: Minimum 92 octane
Oil system: premixed oil and fuel
Cooling system: air-cooled
Reduction gear: cog belt or optional gearbox
Power output: 20 hp (15 kW) at 6000 rpm

230F-22
Cycle: 2
No cylinders: 1
Bore: 69.50 mm
Stroke: 60 mm
Displacement: 228 cc
Cooling: Air
Ignition: Coil
Reduction: Poly-V belt
Reduction Ratio: 2.5-1
Weight: 20 kg
Max pwr: 22 hp at 6500 rpm
Price 1998: 14,000 Fttc

230F-20
Cycle: 2
No cylinders: 1
Bore: 69.5 mm
Stroke: 60 mm
Displacement: 228 cc
Cooling: Air
Ignition: Coil
Reduction: Poly-V belt
Reduction Ratio: 2.04-1 to 3.06-1
Weight: 22 kg
Max pwr: 20 hp at 6500 rpm
Price 1998: 15,500 Fttc

The 215 is a conventional single-cylinder two-stroke engine that weighs 39 lb (18 kg) in its 215R aircraft version. The engine features single breaker and points ignition, with single capacitor discharge ignition used on the current models. It also incorporates piston porting, tuned exhaust system, single carburettor, fan cooling, fuel pump, a cast iron cylinder liner, ball, needle and roller bearings throughout. The 215R aircraft version was offered with an optional belt reduction system and the modern industrial versions have an optional gearbox with ratios of 2.04, 2.65 and 3.06. Starting is a recoil starter with a custom electric starter available as an option.

The basic engine was originally designed and produced by JLO of Germany and was later acquired by the AMW Cuyuna Engine Company of Beaufort, South Carolina and marketed under the Cuyuna brand name. Later the engine was marketed by Cuyuna under the Two Stroke International (2si) brand. Cuyuna no longer markets engines for aircraft use although the 215 was still in production as an industrial and multi-fuel engine.

Variants
215D – Gasoline aircraft engine with direct drive. Single carburetor, 20 hp (15 kW) at 6000 rpm, weight 42 lb (19 kg).
215R – Gasoline aircraft engine with belt reduction drive. Single carburetor, 20 hp (15 kW) at 6000 rpm, weight 39 lb (18 kg).

Specifications

215D
Type: Single-cylinder, two-stroke aircraft engine
Bore: 2.658 in (67.5 mm)
Stroke: 2.362 in (60.0 mm)
Displacement: 214 cc (13.06 cu in)
Length: 11.75 in (298.5 mm)
Width: 7.0 in (177.8 mm)
Height: 14.0 in (355.6 mm)
Dry weight: 42 lb (19 kg)
Components
Valvetrain: piston porting
Fuel type: Regular auto fuel
Oil system: premixed oil and fuel at 50:1
Cooling system: fan cooled
Reduction gear: optional belt reduction
Performance
Power output: 20 hp (15 kW) at 6000 rpm
Compression ratio: 12.5:1