Rotax Type-C Gearbox Removal, Strip, Service, Rebuild, and Refit

Introduction ...

This page is a photographic walkthrough with some explanations along the way of the steps involved in a Rotax Type-C Gearbox Strip, Service, Rebuild, and Refit.



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Here is a mostly complete engine (minus radiator and hoses etc.) removed from aircraft on the workshop bench

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Seen from a few different angles ...

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And a close up of the gearbox itself ...

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Removing gearbox from engine ...


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Start by removing the gearbox cover allen screws ...

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Using a rubber mallet gently prise the gearbox cover off the gearbox housing ...

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Here is the removed gearbox cover on the bench with old gasket still in place ...

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Gearbox housing still in place on engine ...

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Crankshaft locking pin on the bench

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This is inserted in the pulse port and crankshaft rotated until it drops in place. The crank is now locked. It is necessary to lock the crank to remove the allen bolt that is securing the gearset small gear.

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Removing the allen bolt ...

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The allen bolt on the bench ...

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The gearset small gear on the bench ...

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Removing the gearbox housing bolts. There are four external to the gearbox

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Close-up of the loosened external bolts ...

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And there are four internal to the gearbox ...

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Using a telescopic magnet to pull the recessed bolts out ...

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Removed gearbox housing on the bench ...

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A view of the rubber coupling (hardy disk) in place. This purpose of this coupling is to reduce / smooth out the power pulses from the engine that would otherwise be transmitted to the prop and result in excessive gear backlash ...

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Again from a different angle ...

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The jubilee clip used to compress the rubber coupling to facilite removal from gearbox flywheel ...

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Rotax's specialist tool for removing the allen bolts. This is essentially an allen key but with a locator pin on the end as the allen key gripping recess is very shallow ...

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Tightening the jubilee clip around the circumference of the rubber coupling ...

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Using Rotax's tool for removing the allen bolts ...

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The rubber coupling on the bench ...

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The gearbox flywheel exposed on the crankshaft ...

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Removing the securing bolt ...

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Rotax's flywheel removal tool on the bench ...

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Rotax's flywheel removal tool bolted to the flywheel ...

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It may be necessary to apply some heat to expand the flywheel to facilitate it's removal ...

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Tightening the removal tool's centre bolt to pull the flywheel off ...

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The gearbox flywheel on the bench with the removal tool still attached ...

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Flywheel, flywheel removal tool and protection cap on the bench together ...

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The PTO end of the engine with the Rotax Type C gearbox now completely removed. Note the protection cap that is inserted onto the end of the crankshaft to protect it whilst you screwed in the flywheel removal tool bolt ...

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Gearbox strip, service and rebuild ...

Part 1 - Servicing the Gearbox Cover and it's associated components ...


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Rotax Type C gearbox gasked and seal set. These will be used in the gearbox reassembly ...

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Gearbox cover and prop shaft flange ...

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This piece of wood is used to grip the propshaft whilst working on it. It is bolted to the workshop bench ...

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Prop shaft flange located in gripping device and the main gear retaining nut is removed ...

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The nut and friction washer on the bench ...

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The main gear with it's retaining nut removed ...

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The crankshaft protection cap is now reinserted in the end of the crank in preparation for using the long puller to pull the large gear off the taper lock bush.

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The large gear is heated to lossen the taper lock bush retaining compound and to provide some thermal expansion ...

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The long puller is screwed onto the thread on the large gear and tightened until the large gear is pulled off the taper lock bush ...

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The large gear on the bench with the long puller still attached ...

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The large gear on the bench on it's own ...

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A view of the prop shaft with taper lock bush loose on the propshaft ...

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The taper lock bush needs to be expanded to slide it off the prop shaft. This is Rotax's specialist tool for that purpose. Note the splitter bolt that is tightened to prise TLB apart ...

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Here you can see a close up of the splitter end of the bolt ...

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Here you can see the TLB in position with the splitter bolt orientated vertically finger tightened ready to prise the TLB apart ...

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The taper lock bush removal tool mounted on the taper lock bush ...

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The removed taper lock bush on the bench ...

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The prop shaft is then pressed out using a hydralic press ...

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The bearing retaining ring is then removed ...

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Heat is applied to back of gearbox cover for thermal expansion allowing bearing to either drop out or be pushed out ...

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Using Rotax's bearing pusher to push the main beaing and seal out of the gearbox cover ...

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The gearbox cover with all bearings and seals removed ...

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Gearbox housing and gearbox cover together in the ultrasonic bath getting a well needed cleaning ...

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The gearbox cover after cleaning ...

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Using Rotax's bearing seal insertion tool to provide support for the new seal whilst it is reinserted into gearbox cover ...

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Prop shaft and distance ring ready to be inserted into gearbox cover ...

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The distance ring is replaced curved surface facing out toward where propshaft flange will be ...

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Expand the gearbox cover gently by applying heat and drop / push bearing firmly back into place.

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Applying heat to the gearbox cover to drop the other bearing in ...

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Gearbox cover with both bearings back in ...

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Prop shaft with CopaSlip apllied to bearing seat ready to be pressed back into gearbox housing ...

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Prop shaft with CopaSlip apllied to bearing seat ready to be pressed back into gearbox housing ...

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Gearbox cover and prop shaft in the hydraulic press ...

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Force is applied via the steel box section to the centre-ring of the bearing so that the bearing is not stressed during the pressing process ...

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Spreader plate is used to spread the load ...

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The gearbox bearing fully pressed home ...

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Close up of the prop shaft back in place ...

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Torquing up the prop shaft bearing retaining ring allen bolts ...

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The inside surface of the TLB is thoroughly cleaned and Loctite 648 applied to help retain it in position once replaced and also to afford it some protection from corrosion.

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Here the TLB is inside the insertion tool in position ready to release onto the propshaft. It is important that the TLB is correctly replaced. Applying some Loctite 648 and then bashing it back down with a screw driver effectively wipes the Loctite 648 off and there will be none on the actual TLB itself because it all got wiped off further up the prop shaft.

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The taper lock bush in the correct position on the prop shaft ready for replacing the main gear ...

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The main gear back in position ...

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The friction washer and nut is replaced ...

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And the nut torqued up with loctite applied ...

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The gearbox cover and all components reassembled in place ...

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Gearbox housing and gearbox cover together in the ultrasonic bath getting a well needed cleaning ...

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Part 2 - Servicing the Gearbox Housing and it's associated components ...


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Rotax Type C gearbox gasked and seal set. These will be used in the gearbox reassembly ...

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Gearbox housing on the bench with a view of one of it's seals ...

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And the other side of the gearbox housing ...

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Removing the bearing retaining circlip ...

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The bearing retaining circlip removed and also note the shim that must go back on at rebuild ...

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Heat is applied to facilitate removal of bearings and seals. Here are the seals and bearing once removed ...

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A view of the other side of the gearbox with the seals and bearings removed ...

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Gearbox housing and gearbox cover together in the ultrasonic bath getting a well needed cleaning ...

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The gearbox housing fresh from the ultrasonic cleaner ...

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Here is one of the gearbox seals mounted on the Rotax's insertion jig which provides support when the seal is pushed home ...

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Pushing the seal into position ...

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Heating the gearbox housing so that it expands enough to allow the bearing to be dropped back into place whilst being carefully not to direct unnecessary heat toward the seal which could damage it ...

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Bearing dropped back in place and firmly pushed home ...

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Here is the insertion jig for inserting the other oil seal ...

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The seal greased up and ready to re-insert ...

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Pushing the seal home ...

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Oil seal in place ...

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The gearbox housing being heated to accept the other bearing ...

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The other bearing back in place and the groove for the retaining circlip is cleared with air gun so that the circlip can properly relocate once replaced ...

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Circlip re-fitted ...

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The re-assembled Rotax Type C gearbox housing ready for re-fitting once the engine has been re-built ...

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Re-fitting the gearbox to engine ...


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Gearbox flywheel is refitted ...

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Rotax's specialist tool for re-fitting the rubber coupling ...

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What can happen to the bolts if you don't use the correct tool ...

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The rubber coupling is bolted to the flywheel ...

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The Type-C gearbox housing can now be re-fitted ...

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The eight bolts (4 inside and 4 outside) can now be re-fitted ...

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The gearset small gear can now be re-fitted. Note the all important shim that goes behind it. This is to accomodate the offset due to the thickness of the gearbox gasket ...

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The small gear allen bolt is re-fitted and torque'd up ...

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Once the small gear allen bolt is re-fitted the gearbox housing bolts can be torque'd up ...

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Fitting a new gearbox gasket ...

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Here is the gearbox cover together with the main gear mounted on the prop shaft ...

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The gear cover is offered up to the gearbox housing and eased into place. It helps to rotate crankshaft a little to help the main gear and small gear to mesh ...

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Re-fitting gearbox cover bolts ...

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The gearbox is re-filled with gearbox oil and the magnetic plug is safe tied. This engine is refitted to aircraft in an inverted configuration so one inverted the magnetic cap will be at the bottom ...

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If you have a starter motor fitted to your aircraft it is a good idea to disassemble it. Then you can verify the condition of the brushes and give it a good clean paying particular attention to restoring a good connection between the brushes and the commutator. This image is after commutator has been cleaned. The commutator was barely visible before! ...

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Inspect the brushes ...

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Re-assemble the starter motor and re-attach it to the starter cover ...

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Lubricate the starter gear in readiness for the starter cover to be re-fitted ...

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Starter motor cover and starter motor is re-fitted to engine ...

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Here are a few images of the rebuilt engine taken from a few different angles ...

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The engine is ready to re-fit to aircraft ...

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AeroFix Aviation Ltd
Bolton
Lancashire
United Kingdom
BL3 4NN
Telephone: 07779 147 229
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