Rotax, Rotax 503 aircraft engine repair manual.

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Reassembly

Crankshaft installation

Tools required

Ratchet
10 mm socket
13 mm socket
() mm allen wrench
Screw driver
Rubber mallet

Parts required

830 747 PTO seal 1
831 950 MAG seal 1
830 355 0 ring 1
960 951 rubber plugs 5

Note: New model engines use 5, 0 rings but no plugs

Shop Supplies required

Grease
Locktite 515

Seal preparation

Before installing the two seals on the crankshaft first lubricate the interior lip of the seal with a light coating of grease to ensure proper lubrication on initial start up.

Lower Crankcase preparation

To ensure proper seal between the two crankcase halves it is necessary to use a crankcase sealing material. The recommended sealant is Locktite 515 Gasket Eliminator.

Apply a bead of Lock 515 to the sealing surface of the bottom crankcase half. Then using your finger spread it around until all the sealing surface has a light covering.

Upper Crankcase preparation

Turn the upper crankcase halve upside down so that it sits on your workbench on the cylinder head studs. Looking down into the crankcase half you will see 5 holes located directly under the area where the crank bearings ride. Remove the 5 rubber plugs (#960 951 from your gasket set ), and install them in these holes.

Note: Newer engines use 5, O rings instead of rubber plugs.

Crankshaft bearing replacement

Crankshaft preparation

Remove the rubber ring from around the bearing located on the magneto end of the crankshaft. Replace it with a new O (#830 355) ring from your gasket set.

Lubricate bearings, and rod journals.

Crankshaft Installation

Grasping the crankshaft by the ends lift it up and place it into the upper crankcase half. Align the center crankshaft locking rings, into the crankcase cut outs and the 0 ring, and magneto seal with seal alignment grooves in crankcase.

Crankcase reassembly

Tools required

Ratchet
10 mm socket
13 mm socket
() mm allen wrench
Torque wrench

With the crankshaft installed in the upper crankcase, place the lower crankcase onto it. Install the () 13 mm lower crankcase retaining bolts, then the () 10mm head bolts on the 377/447.

On the 503 install the () 13 mm head bolts,then the () ()mm allen head bolts.

Snug the bolts up but do not tighten them.

Stator plate installation

Now we will be installing the stator plate. We will be using the stator plate to proper align the crankcase halves. To install the stator plate, feed the wiring through the hole in the crankcase, then position the stator plate so that the holes in the stator unit line up with the two holes in the upper and lower crankcase halves.

Install the 2 ()mm allen head bolts, and torque them up to () inch lbs. Check the alignment of the two crankcase halves by running your finger along the seam between the two halves. This seem should now be even.

Torqueing the crankcase

Using a torque wrench, and in two stages, torque in an X pattern from the center out the () 13mm head bolts, to () in lbs. then the 4, 10mm head bolts to () inch lbs.

Now repeat the process bringing the ()mm head bolts to () inch lbs. and the () 10mm head bolts to () inch lbs.

Note:

When installing all the lock washers used on the Rotax engines the lock washers should go so that the points at the openings of the washer face towards a disposable part. Thus all the washers should face towards the bolt head, or nut during installation.Crankcase reassembly. On the 503 torque in an X pattern starting from the center the () 13mm head bolts, to () inch lbs. and the () allen head bolts to () inch lbs. Then repeat the process bringing the () 13 mm head bolts to () inch lbs, and the () allen head bolts to () inch lbs. For correct torque pattern refer to Fig (). When complete turn engine over so it is resting of lower crankcase half.

Piston, pin, bearing, clip, base gasket installation

Tools required

Circlip installation tool or flat screwdriver
pair of pliers with rubber coated handles

Parts required

377/447 cylinder flange gasket 850 105 2
503 cylinder flange gasket 831 855 2
wrist pin bearing \s\s 832 904 2
circlips 945 935 2

With the engine in an upright position use an oil can, to squirt oil into the the crank bearing oiling holes. Install the cylinder base gaskets onto the 4 cylinder head studs and slide them down until the are flush against the crankcase.

Piston installation

Move the connecting rod to top dead center. Install the wrist pin bearing (#832 904) into the top of the connecting rod. Using an oil can lightly oil the bearing.

Pickup a piston, with the arrow on the dome of the piston pointing towards the exhaust port of the engine, and the circlip hole with no circlip in it facing outward start the wrist pin into the hole until it just protrudes past the inside boss. Slip the piston and pin assembly over top of the connecting rod and bearing. Looking through the wrist pin hole from the other side align the pin with the bearing and push the wrist pin gently through. With the wrist pin installed, using a new wrist pin clip and installation tool or screwdriver carefully install the clip into the wrist pin clip retaining groove so that the opening in the clip is facing towards bottom of the piston. Repeat the process for the other piston.

CAUTION!

Always torque in two stages, starting from the centre, doing the larger diameter bolts first.

Make sure that the arrow or AUS mark on the dome of the piston is pointing towards the exhaust side of the engine.

Make sure that the base gaskets are installed with the gasket cut outs matching the transfer port cylinder cut outs.Caution

Install the wrist pin clip so that the opening in the clip is facing towards the bottom.

Ring installation

Tools required

Fingers, eyes

Parts required

Top rings 2
Bottom rings 2

With the pistons, pins, and clips installed the next step is to install the rings.

The first ring we will install is the lower ring. Carefully look at the ring in the area of the ring ends. Note that on one side of the ring is writing, this is the top of the ring.

With the writing facing the top of the piston, use you fingers to gently pry the ring over the piston and into the lower ring groove.

Once installed rotate the ring until the opening in the ring aligns with the ring dowel pin.

Now using your fingers install the top ring, and position the opening in the ring so that it also faces the ring dowel.

Once the rings have been installed make sure that they move freely, with no stickiness or seizure.

Repeat the process for the other side

Cylinder installation

Tools required

Pliers with rubber coated handles
hands and fingers

With the rings installed, and properly position in the ring groves, place a pair of pliers with rubber coated handles, so that the connecting rod is between the two handles, slowly lower the piston until the piston skirt is resting on the handles.

Picking up the cylinder and using a lightly oiled rag oil the bottom of the cylinder. Then with the arrow on the piston dome facing towards the exhaust port on the cylinder gently lower the cylinder down over the 4 head studs and onto the top of the piston.

Note: On the 503 engine make sure that the cylinder with the self taping hole for the lower engine shroud is placed on the PTO side of the engine.

With your fingers come in from the sides of the piston and gently squeeze the top ring together until the cylinder slides down over it.

Repeat for the bottom ring. Then slide the cylinder down, while removing the pliers.

Repeat for the other side.

Cylinder head installation

Tools required

Cylinder alignment bar
torque wrench
13 mm socket

Parts required

Head gaskets

Before installation of the cylinder heads it is first necessary to properly align them. If they are not aligned the intake manifold will break or crack, when the manifold is torqued, due to improper hole alignment.

To align the cylinders install the cylinder alignment bar onto the intake manifold side of the cylinders using the intake manifold holes. Snug the bolts up.

Note: The reason for using the intake side of the engine is because it is a machined flat surface, and is not as prone to heat warpage., as the exhaust side.

Once the alignment bar has been installed install the head gaskets, and then the cylinder heads. With the cylinder heads in. place install the 8 flat washers, and then the head nuts. To correctly position the longer nuts place the top cylinder shroud, on the heads with the open end facing the magneto side. Note the position of the longer nuts.

Snug all of the nuts up and then using a torque wrench, torque in an X pattern first one head then the other in two stages. The first stage to () in lbs. the second to () inch lbs.

Note: Use the top cylinder shroud to locate the position of the longer head nuts.

Ignition Timing

Tools required

Flat blade screw driver
Dial indicator
Buzz box or timing light
Feeler gauges
Business card

Parts require

grease for phenolic block assembly

Before installing the fan tower it is first easier to do the ignition timing. During disassembly we marked the stator unit and crankcase half with our hammer and punch. Align this two marks by loosening the two stator plate retaining screws and moving the stator unit. Place your dial indicator into the spark plug hole in the magneto cylinder. Connect your buzz box to ground and to the magneto side coil wire, this is the blue on black wire.

Turning your engine over clockwise bring your piston to top dead centre. Zero your gauge. Turn your buzz box on. Now turn your engine counter clockwise. The Buzz box should \indicate the points are closing at .086 before top dead centre.

Repeat for the PTO cylinder using the blue on red wire.

If the timing is not coming in at .086,BTDC on the mag side cylinder, center your stator plate on the two retaining screws. Gap the points at .015. Turn your engine over clockwise, bring your piston up to top dead centre. Zero your gauge. Hook up your buzz box. Turn the engine counter clockwise and note the firing position.

If the engine is firing to early move the stator plate clockwise.

If the engine is firing to late move the stator plate counterclockwise.

To time the PTO side cylinder insert your dial indicator in PTO cylinder head. Turn the engine over clockwise and bring the PTO piston up to TDC. Zero your gauge. Hook up your buzz box to the blue on red wires. Turn the engine over counter clockwise and note the Ignition Timing firing position. It should be .086 BTDC.

If the points are firing to early increase the point gap on the PTO set of points.

If the points are firing to late decrease the point gap on the PTO side points.

NOTE: the mag set of points are the top set, the pto points are the bottom set with the spark plugs facing up.

With the timing properly set apply a bit of grease to the phenolic block for proper lubrication of the point arms.

Caution:

Before installing the magneto run a business card or similar item through the points when they are closed to remove any grease or foreign material.

For installation of points, and condensers refer to section ().

Rebuilding  the Rotax  377, 447, and 503 ultralight aircraft engines.

Magneto installation

Tools required

Flywheel puller ring # 876 080
Torque wrench
1 1/4 socket or metric equivalent

Before installing the magneto check to make sure that the screws holding the stator unit, points and coils are tight, and that no wires have been pinched or cut during installation.

Fan tower installation

Tools required

() mm allen wrench
torque wrench

Place the fan tower up against the crankcase halves on the magneto side. Align the four holes in the bottom half of the tower with the four holes in the base of the crankcase halves.

Install the 4 ()mm allen head bolts and lock washers.

Torque the 4 ()mm allen head bolts to () inch lbs.

Carefully place the magneto onto the crankshaft magneto end, aligning the magneto key way cut up with the crankshaft key way.

Install your lock washer, onto the crankshaft, with the locking points facing towards the nut, install the nut.

Install the magneto puller ring, with the locking arm positioned into the intake side of the fan tower housing. Snug the puller up with three ()mm bolts.

Using a torque wrench torque the magneto retaining nut to () ft lbs. Remove the magneto puller ring.

WARNING:DO NOT USE LOCKTITE ON THE CRANKSHAFT OR MAGNETO!

NOTE: THE TORQUE ON THE MAGNETO NUT IS GIVEN IN FOOT LBS.

Lower shroud installation

Tools required

Screw driver
13 mm socket
ratchet
() mm allen wrench
torque wrench

Parts required

Intake gaskets 4
Exhaust gaskets 4
377/447 850 190
503 - 850 150

Before installation of the lower shroud(s) it is necessary to install the intake and exhaust gaskets into the lower shroud(s).

To do this bend the retaining tabs located on the inside of the shrouds up, place the gasket into position, and then bend the tabs back down so that they lock the gasket into position. This process is the same on the intake and exhaust gaskets.

Note: Some models do not have this tabs, it may be necessary to use gasket eliminator, or other similar substance to hold the gasket into position.

Once the gaskets have been locked into position place the shroud over the cylinders from the PTO end.

Using gasket eliminator or other similar substance, affix the two remaining intake gaskets onto the intake manifold. Place the manifold up against the lower shroud intake side.

Place the 4 bolts used to retain the manifold into the appropriate holes, and snug the bolts up.

Caution:

Make sure that the gaskets have not been allowed to slip down before bolt installation.

Torque the bolts in an X pattern from the centre out to () inch lbs.

Repeat the process for the exhaust manifold side,

Torque the 4 ()mm allen head bolts on the exhaust to () inch lbs.

On the 503 engine their are two shrouds. These can be installed using the above technique. There is also a 10mm head self tapping bolt that needs to be installed on the PTO end side of the intake shroud.

CAUTION:

Note that the two longer bolts used to secure the intake manifold are similar to some bolts used on the lower crankcase. It is possible to use the incorrect bolts, if not careful.

Upper shroud installation:

Tools required

Screw driver
13 mm socket
ratchet
torque wrench

Place the upper shroud over top of the cylinder heads. Carefully lower it into position. The upper shroud should over lap the lower shroud and the screw heads and washers holding the two together should be on the outside of the upper cowling. On some models of the 377/447 there is an aluminum bar between the two screws located on the PTO end screws. The top cowling should fit underneath this bar.

With the cowling in position and properly lined up, snug up the screws.

Next install the 3,(4 on the 503) 13 mm head bolts and washers into the holes in the top cowling. Snug these up, and then torque them to () inch lbs. Be careful not to over torque or you will end up tightening up the head nut.

Caution:

The torque on the these nuts is less than that of the head nut.

Tighten up the screws fastening the upper and lower cowl together.

Note: The lower cowl fits into the fan tower housing, while the upper cowl fits outside of the fan tower housing.

Fan pulley and recoil cup installation

Tools required

() mm allen wrench

Prior to installing the fan pulley install the fan belt. To do this place the belt through one blade of the fan and rotate it until it is installed in the fan tower.

CAUTION:

MAKE SURE THE FAN BELT IS INSTALLED IN THE SAME ROTATION AS IT WAS REMOVED.

Now position the belt into the lower fan pulley and pull it down and into position on the magneto. Align the three holes. Install the recoil cup. Install the three ()mm allen head bolts and lock washers.

Note: When installing all the lock washers used on the Rotax engines the lock washers should go so that the points at the openings of the washer face towards a disposable part. Thus all the washers should face towards the bolt head, or nut during installation.

Install the locking pin into the impulse hole and lock the crank. Torque the 3, ()mm allen bolts to () inch lbs.

Remove the locking pin.

Check the belt tension. If loose refer to section (), fan belt adjustment.

Coil and wiring installation

For ease of disassembly we removed the lower coil. To reinstall the coil. Reconnect the wiring, in the same order as removed. Reconnect the coil ground wires, and bolts, using blue locktite on the bolt threads.

Reconnect the ignition suppressor box.

Install the rubber grommet protecting the wiring as it exists the crankcase.

Recoil installation

Tools required

10 mm socket
ratchet
torque wrench

Place the recoil into position over the recoil cup. Align the 4 holes in the recoil with the 4 holes in the casing. Install the 4 10mm head bolts, and lock washers and torque to () inch lbs.

Note: The location of the recoil in relation to the engine installation.

Fan cover installation

Place the fan cover so that the two tips, and the three clips line up with the appropriate holes. Gently push the cover on making sure that the clips lock into position.