• All links lead to the English pages of the wiki. Five articles are so far only available in German – they are marked DE ONLY and link to the German page.
• Many articles show real damage found in the workshop and explain how it happened.
• Footnotes in the texts often contain important additions.
• Each page can be saved individually with the “Export PDF” tool.
• Some modifications described are not approved – the Rotax documentation always takes precedence.
• Questions, topic suggestions or corrections to wiki@kleinjung.de.

Everything about the Bing 64 constant-velocity carburetors: adjustment, synchronisation, wear parts and typical faults.

01 The return line in the fuel system 912 914
Why the fuel pressure for the Bings has to stay between 0.15 and 0.5 bar and what the return line does – with reference to the Installation Manual.

02 Darker spark plugs on one side 914
A case study: a machining edge in the choke housing left over from production caused a rich mixture on one side of the engine for years.

03 Setting the idle mixture without an exhaust gas analyser 912 914
A guide for experienced mechanics on setting the idle mixture with a synchroniser and an accurate tachometer.

04 Synchronising the carburetors on the 912 and 914 912 914
Step by step: preparation, idle, cable adjustment – how to synchronise the carburetors on a warm engine.

05 Centring the throttle valves of the Bings 912 914
An often overlooked fault in carburetor overhauls: how an off-centre throttle valve upsets the transition and how to set it correctly.

06 The needle jet 912 914
Why the needle jet wears faster than expected – with examples after 206 and 971 operating hours.

07 Special parts for the Bings Parts
Supplier and part numbers for replacement floats, float bowls, valve seats and atomisers from BMW motorcycles (not genuine Rotax parts).

08 Replacing the float needle valve seat bushing 912 914
Why carburetors overflow when parked (not because of the tailwheel!) and how to replace the valve seat bushing.

09 The transition bores 912 914
Basics of the transition bores and an experience report on an (unapproved) modification on the 912 ULS and 914.

10 Altitude compensation on the Bing 64 912 914
Explained in detail: the Bing 64 carburetors on the Rotax have no altitude compensation – with a technical bulletin from Bing.

11 Differences between the 912 and 914 carburetors 912 914
The three carburetor types for 80, 100 and 115 hp and how their jets and design differ.

12 How the carburetor components interact Basics
Two charts show which carburetor component affects mixture preparation in which load range.

Intake system and air routing.

13 Airbox or not? 912 914
Three reasons why an airbox always makes sense from the engine's point of view: cooler intake air, carburetor heating and calmer carburetors.

Ignition modules, pickups, spark plugs and the internal generator.

14 Ignition modules – suddenly both faulty 912 914
Why both modules never fail at the same time and how the cut-in speed reveals a creeping defect.

15 How the soft-start modules work 912 914
A short explanation of the soft-start modules fitted since late 2014 and their ignition timing during starting.

16 Troubleshooting the ignition system 912 914
Compact workshop basics: pickup arrangement and gap, assignment to the plugs, connection and resistance of the ignition coils.

17 … always black spark plugs 912 914
Why the plug appearance on a carbureted engine is usually misleading after landing and taxiing, and when a check makes sense.

18 Overview of the spark plugs used Table
Table of NGK spark plugs and tightening torques for Rotax two- and four-stroke engines, plug caps and the designation code.

19 Cleaning the spark plugs 912 914
Which of the many cleaning methods can damage plugs – and why replacing them is often the better choice.

20 Checking the internal generator 912 914
Testing the charging and lighting coils with an ohmmeter – easier than described in the manual.

Components on the ignition housing and the water pump.

21 The leakage bore on the ignition housing 912 914
Where the well-hidden leakage bores of the water pump are located and what escaping fluid means.

Propeller gearbox, slipper clutch and crankshaft locking.

22 Lubrication of the hollow propeller shaft 912 914
How the splines are lubricated on the hollow propeller shaft – with drastic damage pictures and Rotax's solution.

23 Locking the crankshaft correctly 912 914 Maint.
How to use the locking screw without bending the locking pin – and so avoid having to strip the engine.

24 Thrust washer 33.2/51/1.2 P/N 827992 912 914
Diagnosing a broken or missing plastic thrust washer in the gearbox from the friction torque in the free play, and what to do about it.

Displacement parts, oil consumption and sealing.

25 Detecting increased oil consumption 912 914
A systematic approach: check the oil level correctly, record the consumption and find out where the oil goes.

26 Leak at the cylinder base 912 914
In most cases a small O-ring (P/N 431570) is missing – cause and remedy.

Valves and valve seats.

27 Oval intake valve seats 912 914
Why action should be taken from 10 % leakage, even though the manual allows 25 %.

Oil level, oil pressure and oil pressure senders.

28 Checking the engine oil level correctly 912 914
How to check the oil level: when to check, how to turn the propeller and what clubs need to watch out for.

29 Constant oil pressure fluctuations in operation 912 914
Why the oil pressure flickers at certain rpm: resonances in the oil pump and pressure relief valve – and what can be done.

30 Checking the old VDO oil pressure sender 912 914
Test procedure with nominal resistances for the mechanical sender, which is no longer covered in newer manuals.

See also: Detecting increased oil consumption (25)

Coolant hoses and heat exchangers.

31 Length of the coolant hoses Table
Hose lengths for supply and return per cylinder – useful for the 5-year inspection.

32 Heat exchangers on Rotax aircraft engines 912 914
Pros and cons of a coolant-to-oil heat exchanger from a practitioner's point of view.

Download the German-language Line Maintenance checklist for the 912 and 914 here (complete, or in two parts with an XLSX cover sheet).

33 Material for the 5-year inspection Parts DE only
Parts list with Rotax P/N, quantities and alternatives for the 5-year inspection, including extra parts for the 914.

34 The crankshaft breakaway torque 912
Background on the breakaway torque of the 912 S/ULS: forces, damage pattern, when action is needed and what the new crankshafts change.

35 Tightening torques Rotax 912/914 – Maintenance Manual Heavy NEW Table
Comprehensive table of all tightening torques from the Maintenance Manual Heavy (Ed. 2 / Rev. 1, Nov 2025), sorted by ATA chapter – with thread, Nm, in.lb/ft.lb, locking, page reference and notable points in the manual.

36 Frequently used tightening torques 912 / 914 Table
Table of tightening torques and Loctite specifications for repairs, including the cylinder head tightening procedure.

See also: Locking the crankshaft correctly (23), Wear limits for overhaul and repair (56)

Field-proven home-made tools.

37 Gauge for setting the float level Tool
A self-developed gauge that shows the float level of the Bings in mm and lets both arms be compared.

38 Tool for the float needle valve seat bushing Tool
Dimensions and design of a simple puller/press tool made from two turned parts.

39 The piston support Tool
A simple tool made from two plastic bars that holds the piston while the cylinders are fitted.

What has a positive effect on operating the Rotax.

40 Exhaust gas values at the tailpipe 912 914
Exhaust values of the 912S and 914 measured on the test bench after overhaul, for orientation.

41 Setting the right power 912 914
In detail: power, wear and cost in context, fixed-pitch and variable-pitch propellers, and power settings in percent.

42 Operation in very cold conditions 912 914
Oil selection, viscosity and Rotax specifications for starting in severe cold.

See also: Heat exchangers on Rotax aircraft engines (32), … always black spark plugs (17), The crankshaft breakaway torque (34)

Turbocharger, TCU, wastegate and diagnostic software of the Rotax 914.

43 The turbo switch on the 914 914
What the mysterious “Turbo” switch is really for and why using it wrongly can cost a crankshaft.

44 A faulty wastegate servo 914
What the TCU warning lamps indicate, how a servo defect is detected and what the consequences can be – with logged data.

45 The B.U.D.S. software 914
Experience with BRP B.U.D.S. Aircraft: easy access to the TCU, but far fewer log lines per second than TLR 4.6.

46 TLR 4.6 – the “old” TCU software 914
How to run the old DOS program with a USB adapter: configuration, log files, reading data and calibrating the TPS.

47 The turbocharger cool-down run 914
An oil trail and its cause: what happens if the cool-down run is cut short, and how to fix it.

48 The check valve on the turbocharger 914
Smoke when starting and an oil stain under the aircraft: cause in the check valve and rework of the banjo bolt.

49 Wastegate position at full throttle 914
Test bench data show from which rpm the wastegate is fully closed at 115 %.

50 Float chamber vent hoses 914
How the pressure ratio works on a turbocharged carbureted engine and which faults cracks, valves or a misadjusted pitot tube cause.

Rotax manuals, technical bulletins and how to find them.

51 The technical bulletins in German Download DE only
Archive of the last German-language manuals (as of 2013) and technical bulletins – for information only.

52 Finding documents at Rotax 912 914
How to find the right SBs and manuals for an engine serial number on flyrotax.com.

53 Why Rotax documentation is now English only Info DE only
Background to SL-912-018: since 1 Sept 2016 manuals and SBs are published in English only.

Recommendations for useful accessories.

54 Engine pre-heater for cold days DIY
A DIY design from the UL forum: a 2000 W ceramic heater for about €65, with build instructions and safety notes.

Useful things around buying, troubleshooting and reference.

55 Checklist for buying an aircraft 912 914
What to check before buying a used aircraft or engine – from the paperwork to an engine run with mag check.

56 Wear limits for overhaul and repair NEW
The formula and tables from the Heavy Maintenance Manual used to decide whether a part has to be replaced.

57 Question list for troubleshooting in a forum Info
Which details about aircraft, engine and maintenance to give when asking for help in a forum.

58 Price and weight comparison of the Rotax 4-stroke engines 912 DE only
912 ULS vs 912 iS: comparable prices and weights, plus pros and cons of carburetors and fuel injection.

59 The Rotax FlyDat 912 914
The three FlyDat versions, available software, manuals and error codes.

60 Downloads of technical documents Download
A collection of technical documents, e.g. on recognising piston damage.

61 Tap drill sizes for metric ISO threads Table
Short table of tap drill sizes to DIN 13 from M1 to M64.

62 Dictionary of aviation abbreviations Lexicon DE only
Extensive A–Z reference with abbreviation, meaning and German explanation.

Where to get parts and what they are called.

63 Part numbers of the copper sealing rings Table
Rotax P/N, size and location of all copper sealing rings used on the engine.

See also: Special parts for the Bings (07)

A collection of links to further pages about engine technology.

links

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