4-stroke general

To search for parts or accessories click on the SHOP tab (left) and search in the shop.

rotax 4-stroke - general

912UL, 912A, 912F, 912ULS, 912S, 914UL and 914F Engines

tightening torques for 912 & 914 series engines

All information provided here is correct at the time of publishing to the best of our knowledge, but Rotax recommendations may change at any time without our knowledge. It is the engine owners responsibility to ensure that the engine is fit for flight at all times. The information is provided here free of charge and with no obligation from us to the consumer. To ensure that you have the correct and most up to date information, you should refer to the current Installation, Operators and Maintenance manuals for your engine. The information provided here may not be valid for aircraft outside the UK. Click here for ConAir SportsTerms& Conditions, including website usage policy.

We have collated the following as a helpful guide, but recommend that you also refer to Rotax manuals and parts lists for correct tightening torques.

Standard Torques	Fastener size / type	Torque Nm
Standard Torque	M4	4
Standard Torque	M5	6
Standard Torque	M6	10
Standard Torque	M8	24
Standard Torque	M10	35

Service Items	Fastener type / size	Torque Nm & Angle	Sealant / Locking (Loctite or wire)
Crank locking bolt blanking screw	M8	15 Nm	Copper washer
Magnetic plug	M12	25 Nm	Wire
Oil filter		Touch + 270º
Spark plugs	M12	20	Heat sink
Oil tank drain plug	M12 bolt	25 Nm	Copper washer / wire
Carb top	M5 bolt	5.5 Nm
Carb needle	M10 fixation screw	Feel (3.5 Nm is good)	Patch on bolt
Throttle lever	M8 nut	5 Nm
Choke lever	M8 nut	5 Nm (care not to break housing)
Carb socket clamp	M5 bolt	2.5 Nm
Fuel block banjo	M8	10 Nm
Banjo on fuel regulator		15 Nm	Copper washer
Carb float bowl 914		5.5 Nm	Wire O ring or fibre washer

Most common items	Fastener type / size	Torque Nm & Angle	Sealant / Locking (Loctite or wire)
Throttle cable clamp bolt	M5	4 Nm
Carb socket bolts	M8 bolt	15 Nm	221 or 222
Fuel pump	Nuts (914 bolts)	15 Nm	243
Magneto cover	M6 bolts	5 Nm	221 or 222
Oil pressure sender		10 Nm	243
Oil pressure sender	M3 wire	1 Nm
Pressure relief valve plug screw	M12	15 Nm (oily)	Wire
Head	M8 nuts (with thread along studs)	10 Nm + 180º
Head	M8 nuts (with plan shank studs)	22 Nm
Head water outlets	M6 bolts	10 Nm	O ring
Inlet manifolds	M6 bolts	10 Nm	O ring
Exhaust stud	M8	8Nm	2701 or 648
Exhaust nut	M8	12 Nm - 20 Nm
Ignition	Plug cap	Hand tight	Cable tie
Rocker cover	M6	10 Nm
Engine suspension frame to engine	M10	40 Nm	O rings
Hose clamps	Sprung	N/A
Hose clamps	M4 screw	Feel
Gearbox housing			574 or 5910
Gearbox housing	M6 bolts	10 Nm
Gearbox housing	M8 bolts	24 Nm

Other useful items	Fastener type / size	Torque Nm & Angle	Sealant / Locking (Loctite or wire)
Crankcase banjo	M16	30 Nm	221 or 222
Gearbox gear	M30 LH nut	200 Nm	648
Oil pump	M6	10 Nm
Banjo govenor / blanking bolt	M10	17 (12 oily)	copper
Banjo bolt 914 scavenge		12
SMD module	M8 bolt into crankcase	24	221 or 222
SMD module	M6 nut	10 Nm
SMD module	M5 bolt	2.5 Nm	221 or 222
Oil tank outlet hose nipple		25
Servo nipple 914	M4	2.5 Nm
Crankcase blank (banjo)	M16	35 Nm	221 or 222 & wire
Crankcase drain	¾ - 16 UNF	25 Nm	243
External alternator	M10	40 Nm
External alternator	M8	22 Nm
Fuel block clamp bolt	M5	6
Sprag clutch	Taper		221 or 222
Sprag clutch	M34 LH nut	120 Nm	648
Magneto housing			574 or 5910 & O ring
Magneto	M6 bolts	10 nm	243 ( 1 bolt only)
Trigger screws	M5 screws	6 Nm
Stator	M5 screws	6 Nm
Remote aluminium box lid	M5 screws	Hand tight
E start	M5 bolts on Mag housing	6 Nm
E start	M5 nuts	6 Nm
E start	Clamp	2.5 Nm
E start terminal	M6 nut	4 Nm
E start solenoid	M6 nut	4 Nm
Flywheel	Taper		221 or 222
Flywheel	M16 bolt	45 Nm + 180º
Mag ring	M6 bolt	10 nm	221 or 222
Trigger bolts	M5	6 Nm
Water pump housing	M6 bolts	10 Nm	1 with copper washer
Impeller	M8	15	221
Gearbox bearing	M7	15 nm	221 or 222
Oil hose nipple	M14	15 Nm	243
Oil filter nipple		60 Nm
Temp sender		7 Nm	243
Blanking banjo bolt	M10	10	Copper washer / 243
Adaptor	¾ - 16UNF	25	243
Piston	Piston pin	Monohook circlip
Cylinder	Studs	3 Nm	O ring
Head water outlets	Tube thread into plate	Position only	648
Temp sender	M10	7	243
Oil tank 914 banjo	M10	17	Copper washer
Oil tank plug screw	M10	17	Copper washer
Vac pump stud	M6	5 Nm	221 or 222
Hydraulic govenor plug screw	M8	10 Nm	221 or 222
Hydraulic govenor	M10	17 Nm
Govenor flange to case	M6	10	221 or 222
Fuel block blank	M10	15 Nm	221 or 222
914 air box hose nipple	M6	3 nm
Fuel regulator mounting screw	M6	8 nm
Air box temp probe		15 Nm	221
Cap lock nut fuel regulator		5 Nm	243
914 turbo and exhaust	M8 stud	6 Nm	2701
914 turbo and exhaust	M8 bolts and nuts around turbo	25 Nm
914 turbo and exhaust	M10 bolt	40 Nm
914 muffler clamp	M8	15 Nm
912 valve housing (top of turbo)		25 Nm
912 banjo oil inlet		10 Nm
912 servo central bolt	M5	6 Nm
Oil cooler nipple	M14	22 Nm
Oil cooler adaptor	M18	35 Nm
Oil cooler bent socket		25 Nm
Oil cooler angular tube	M14	22 Nm
Oil cooler adaptor	¾ - 16 UNF	35 Nm

engine specifications

Rotax 912UL A/F engine

• 80HP

• 4 cylinder

• 4 stroke

• 1211cc

• 8 valves

• 9.0:1 compression ratio

• Normally aspirated with twin Bing constant depression carbs

• Engine supplied with dual electronic CDI ignition, integral 2.27 reduction gearbox,

250W AC electrical generator

• Engine weighs 55Kg

• The engine can easily be identified by the Black rocker covers

• First serial production started in 1989

serial number position

ENGINE - The engine identification plate will contain details of the engine TYPE as well as its unique serial number. The plate should be either Black which is used on non certified engines, or Red which is used on Certified engines. The Engine identification plate can be found either on the magneto housing behind the carburettor for cylinders 2/4 (earlier engines) or on top of the magneto housing (later engines).

technical data

Technical data for 912 & 914 series engines is available on www.rotax-aircraft-engines.com . Click on the engine type at the bottom right hand corner of the homepage to see links to download technical data, performance data, fuel flow graphs and outline drawings.

GEARBOX - The gearbox part number should identify the gearbox specification such as reduction Ratio, gear set width, and

identify whether it has a slipper clutch or not.. The specification is occasionally altered and the part number is not amended, so

do not rely on the part number. The serial number of the gearbox assembly is etched on the outside. Early gearbox’s did not have any part numbers on them.

tightening torques for 912 & 914 series engines

serial number position

technical data

engine specifications

Rotax 912ULS / S engine

• 100HP

• 4 cylinder

• 4 stroke

• 1352cc

• 8 valves

• 11.1:1 compression ratio

• Normally aspirated with twin Bing constant depression carbs

• Engine supplied with dual electronic CDI ignition, integral 2.43 reduction gearbox,

250W AC electrical generator

• Engine weighs 56.6kg

• The engine can easily be identified by the Turquois rocker covers, although it

can occasionally found fitted with Blue rocker covers (these engines were specifically destined for the French market where the engine has been rated differently to comply with the French regulations)

• First serial production started in 1998

Rotax 914UL/F engine

• 115Hp

• Produces 100HP @ 16,000’

• 4 cylinder

• 4 stroke

• 1211cc

• 8 valves

• 9.0:1 compression ratio

• Turbo charged twin Bing constant depression carbs

• Engine supplied with dual electronic CDI ignition, integral 2.43 reduction gearbox,

250W AC electrical generator

• Engine weighs 64Kg

• The engine can easily be identified by the Red rocker covers

• First serial production started in 1996

• The 914 uses a Turbo charger to boost what is basically a 912 engine to 115Hp. The engine uses a simple Turbo control unit TCU to alter the waste gate position to give sufficient boost pressure to achieve max power at altitudes of 16,000Ft. Without this type of control the boost at ground level would be too much and it could lead to permanent engine damage

good operating practices

Where possible use unleaded fuels. Carefully balance carbs. Maintain you engine in accordance with current Rotax Maintenance Manuals and carefully record work carried out.

Successful operation of 912/914 series engines depends on understanding that it is different from conventional aircraft engines. The basic difference is that the 912/914 series engines are geared engines designed to run at 5500 rpm. Conventional aircraft engines are direct drive and run at about 2500 rpm.

The gearbox is designed to handle the huge forces resulting from a propeller being coupled to pistons, but the engine still needs to be treated properly to ensure longevity and reliability.

Smooth & steady reduces gearbox wear.

Avoid low idle speeds - at idle the piston pulses are more pronounced and the gearbox has to deal with a lot of pulsing. This is worse when compounded by the weight of a prop.

Listen to your engine and operate it where it feels right.

Avoid high rpm on cold engines - use a Thermostasis Oil Thermostat to speed up warm up and to stabilise temperatures during descent.

Keep it clean - 912 series engines don’t usually leak, so if there is a leak then there is something wrong - keep the engine clean to help you notice any leak that might be developing.

Always gurgle the engine and check oil level before starting.

Crank engine with mags off to obtain oil pressure before starting.

i want to know more

I want to know more

There is lots more information on the technical pages of this website, but if you still want to know more, why not consider our training courses.

who’s who

ROTAX - are the engine manufacturer

SKYDRIVE - are the UK Distributor for ROTAX aircraft engines

CONAIR SPORTS - are Skydrives SERVICE CENTRE for ROTAX Engines, we also provide Technical support for ROTAX engines supplied in the UK through Skydrive.

ROAN - Rotax Owners Association Network - run by the Canadian Rotax dristributor, this website provides a very good email service for ROTAX Service Bulletins and educational information as well as product reviews.

buying a used 912 series engine, what should I look out for?

PROPER MAINTENANCE RECORDS - including explicit log book entries and worksheets. Find out if maintenance has been carried out by trained personnel, click here.

SERVICE BULLETIN COMPLIANCE - some costly service bulletins to look out for include TBO upgrades, stator replacement, rocker arm replacement, valve spring retainers, pushrod & rocker arm, gearset replacement.

TBO LIFE - could be anything from 600 hours to 2000 hours (10 years to 15 years) depending on engine serial number. Some TBO upgrades need some fairly significant changes which can be costly I.e. The 600 to 1200 hour and the 1500 to 2000 hour upgrades.

GEARBOX SERVICING - is often overlooked, check that the gearbox has been serviced at the appropriate intervals which can vary depending on slipper clutch etc.

COLD STARTING - problems starting from cold could indicate a possible sprag clutch issue.

FUEL TYPE - engines that have been run on fuel containing lead, such as Avgas 100LL, need additional servicing and the lead produces increased deposits that can be harmful to the engine, especially if the engines is then taken out of service for any length of time.

OVERHEATING - look for damaged or missing temperature sensors or blowing head joints which could point to an engine that has been overheated. This is usually very expensive to rectify.

REPLACEMENT PROPS - look for evidence of propeller replacement and enquire why this has been carried out. Even if the engine is fitted with a slipper clutch it must undergo a Shock Load Test in the even of a prop strike, however insignificant it may seem (like hitting the hangar door).

GENUINE PARTS - ask for receipts and check that all parts used are genuine Rotax parts. “Parts for Rotax” are not necessarily genuine, look for “ROTAX PARTS”.

STOLEN ENGINES - ask for proof of ownership and check the serial number against the list of stolen engines available to download at www.rotax-aircraft-engines.com

PARTS INCLUDED - make sure all the bits are there....oil tank, rectifier regulator, starter solenoid, manuals, tool kit.

LONG TERM STORAGE - long term storage is often a bad thing, the engine internals corrode and is more susceptible to failure. If an engine has been in long term storage some checks need to be done, click here & scroll to the bottom for details.

ENGINE SPECIFICATION - check the specification of the engine against your requirements, some items may be expensive to remove or to retrofit. Engines may or may not be installed with: coolant expansion tank; air guide hood; slipper clutch; mechanical tacho; hydraulic govenor; collar nuts; vac pump / vac pump drive. You also need to check starter motor type (standard or large), prop shaft type and prop mounting configuration.

OVERHAUL - check our page on overhaul to see what work should have been done and what parts should have been replaced, and check that the worksheets show that this has been done. Click here.

buying a used 912 series engine, what should I look out for?

Engine serial number position (earlier engines)

Engine serial number position (later engines)