Cuyuna 430

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.

McCornack settled on a 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 {{convert|32|mm|in|2|abbr=on}} Mikuni carburetor, amongst other modifications. The original snowmobile engine produced {{convert|40|hp|kW|0|abbr=on}}. 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 {{convert|30|hp|kW|0|abbr=on}} 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 {{convert|2.362|in|mm|1|abbr=on}} bore version called the 340. The modification reduced its displacement to 339 cc and output to {{convert|25|hp|kW|0|abbr=on}} at 5500 rpm. The standard 430 has a bore of {{convert|2.658|in|mm|1|abbr=on}}.

;340D

:Direct drive version, {{convert|25|hp|kW|0|abbr=on}} at 5500 rpm, recoil starter.

;340R

:Reduction drive version using a belt drive system, {{convert|25|hp|kW|0|abbr=on}} at 5500 rpm, recoil starter

;430D

:Direct drive version, {{convert|30|hp|kW|0|abbr=on}} at 5500 rpm, recoil starter.

;430F

:Reduction drive version using a 3:1 gearbox system, dual carburetors, producing {{convert|45|hp|kW|0|abbr=on}}.Cliche, Andre: Ultralight Aircraft Shopper's Guide 8th Edition, page D-17. Cybair Limited Publishing, 2001. {{ISBN|0-9680628-1-4}}

;430R

:Reduction drive version using a belt drive system, {{convert|30|hp|kW|0|abbr=on}} at 5500 rpm, recoil starter

;UL II

:{{convert|35|hp|kW|0|abbr=on}} version

{{columns-list|colwidth=30em|

• Advanced Aviation Cobra
• Advanced Aviation Husky
• Airborne Avenger
• Airmass Sunburst
• American Aerolights Eagle
• Chandelle Mk IV
• Eastern Ultralights Snoop
• Fletcher Hercules
• Goldwing Ltd Goldwing
• Goodwin Tri-Moto
• Hovey Delta Bird
• International Ultralite Banchee
• Kolb Ultrastar
• LEAF Trike
• Manta FX-3
• Meadowlark Ultralight Meadowlark
• Mitchell Wing P-38
• Pinaire Ultra-Aire
• Pterodactyl Ascender
• RagWing RW4 Midwing Sport
• Robertson B1-RD
• Rotec Rally 2B
• Star Flight Tristar
• Swallow Aeroplane Company Swallow B
• Ultra-Fab Sundowner
• Vintage Ultralight SR-1 Hornet
• Waspair HM 81 Tomcat

}}

{{pistonspecs|

|ref=Cuyuna & McCornack

|type=Direct drive two-stroke piston aircraft engine

|bore={{convert|2.658|in|mm|0|abbr=on}}

|stroke={{convert|2.362|in|mm|0|abbr=on}}

|displacement=428 cc (26.11 cubic inches)

|length=

|diameter=

|width=

|height=

|weight={{convert|65|lb|kg|0|abbr=on}}

|valvetrain=

|supercharger=

|turbocharger=

|fuelsystem=

|fueltype=Regular auto fuel

|oilsystem=40:1 premixed fuel and oil

|coolingsystem=fan forced air

|power={{convert|30|hp|kW|0|abbr=on}}

|specpower=

|compression=12.5:1

|fuelcon=

|specfuelcon=

|oilcon=

|power/weight=0.46 hp/lb (0.76 kW/kg)

|designer=McCornack/Cuyuna

|reduction_gear=

|general_other=

|components_other=

|performance_other=

}}

{{aircontent

|see also=

|related=

|similar aircraft=

|lists=

}}

{{Reflist}}

{{2si}}

Category:Air-cooled aircraft piston engines

Category:Two-stroke aircraft piston engines