Rotary valve shaft replacement, Rotax 532 Rotary valve shaft replacement, Rotax 532 aircraft engine rebuilding manual.



Rotax Engine Service - Rotax Engine Parts - Rotax Engine Rebuilding Workshops!

Rebuilding  the Rotax  532 ultralight aircraft engine.

UltralightNews Ultralight Aircraft Advisory:
 All ultralight aircraft powered by Rotax 532, 582 and 618 aircraft engines.

Problem area: Rotary valve shaft and rotary valve shaft seals.

Incident report: A number of ultralight pilots have reported failure of the rotary valve shaft and seals on their liquid cooled Rotax aircraft engines.

First indications of this are discolouration of the rotary valve oil, found in the rotary valve tank. The oil changes from its normal colour to a white milky colour.


In 1984, Rotax introduced the liquid cooled engine into it's aircraft engine line, the 532 Rotax which was later updated to the 582. Both the  532 and 582 uses a 50/50 mixture of Glycol (antifreeze) and distilled water.

Note: While this is the recommended mixture - for COLD climates - in warmer climates or seasons - mixtures of 10% anti freeze to 90% distilled water can be used. This will aid in lowering coolant temperatures - anti-freeze is NOT an effective coolant! It is used to prevent freezing and supply lubrication to the system. 

Experience has shown that a mixture of 10% antifreeze can drop temperatures as much as 30 degrees versus 50% - in some applications.

Do not use tap water - garden hose water -  water from a water softener, or from a well! 
The chemicals in water will cause corrosion of the internal metal parts of the engine. Including the rotary valve shaft, cylinder head, and cylinders.

The use of any water other than distilled will cause deposits to form on the  rotary valve shaft, causing seal failure. It  can also  prevent the transfer of heat from the cylinder to the water jacket, and corrosion in the cylinder head can cause lack of sufficient coolant flow.

However there have been some reported problems even when operators  have been  using distilled.  This drove the engineers in Austria nuts for a while because there were virtually no reported cross shaft leakage problems in Europe, until someone realized that virtually all antifreeze in Europe is phosphate/silicate free while the North America is still using phosphates and silicates in antifreeze, apparently as some sort of blending agent.  Thus if you  are using regular aluminum compatible antifreeze and distilled water,  you may still have a rotary valve shaft problem.  This usually shows up as  white residue in the radiator overflow lines and bottle. 

A recommended anti freeze is Havoline extended life antifreeze it is  a silicate free antifreeze.

Rotax 532 in field rotary valve shaft replacement

Carburetor removal / coolant & rotary valve tank draining

Tools Required
Small Phillips screw driver
Blade screw driver

Coolant draining

Drain engine coolant at lowest spot possible, into a clean container.

Carburetor removal

sift still connected use a blade screw driver and remove air cleaner(s) from carburetors. Then using a Phillips screw driver loosen clamp retaining carburetors to rubber intake manifolds. With the clamp loose gently pry down and back on carburetor and it will come free of manifold.


Never work on a hot engine! Severe injury can result!\


This Procedure is only to be used to replace damaged rotary valve shaft, if brass gear is damaged engine must be dismantled.

Rotary valve shaft replacement-Draining tank

Tools Required.
-13 mm deep reach socket
-blade screw driver

Shop supplies
Oil drain pan

Before removing the rotary valve tank bracket, it is first necessary to drain the rotary valve tank. On early model engines it will be necessary to remove the hose connected to the tank, from the outlet located directly below the carburetors, on an engine installation where the spark plugs are facing up. To do this take a blade screw driver, and loosen the hose clamp, then using the screw driver, while exerting pressure gently remove the hose from the outlet. This will allow the oil to drain from the engine and rotary valve tank.

On new model engines there will be a drain plug (13mm socket head) located directly below the water pump housing on the exhaust side of the engine. Removal of the drain plug will allow the oil to drain from both the tank and engine.


Once the rotary valve tank hose, or the drain plug, is removed the rotary valve oil will spill out.

Rotary valve shaft replacement- .bracket removal

Tools Required
.-10 mm deep reach thin walled socket
-13 mm deep reach socket
-Blade screw driver

Rotary valve tank bracket removal

Using a 13 mm deep reach socket remove the two top bolts retaining the rotary valve cover plate to the engine. Loosen but do not remove the two lower bolts.

Using a 10 mm deep reach thin walled socket remove the two 10 mm nuts, flat washers and lock washers holding the water outlet socket in place. It may be necessary to push gently over on the rotary valve hose to allow placement of the socket.

With these removed gently tilt the rotary valve plate outward, then using a blade screw driver loosen off the clamp holding the rotary valve hose to the top engine outlet. With the hose removed the complete bracket with coils will now come clear of the engine.

To remove the bracket completely, disconnect the two wires running the ignition suppressor box, and the two leads running to the top of the coils. Next remove the nut from the back of the bracket Remove two top bolts, lock washers and flat washers.

Push over on hose to allow socket placement.

Loosen but do not remove two bottom bolts.

Rotary valve shaft replacement -bracket removal

With all the wiring removed the plate should be completely free from the engine.

Tools Required
13 mm socket

Rotary valve plate, valve, and snap ring removal

To completely remove the rotary valve plate remove the two remaining bolts from the bottom of the plate. Carefully lift the cover off. Remove the rotary valve, wrap it in cloth, and store in a safe place

. Be careful not to loose or damage large sealing 0 ring.

Using snap ring pliers remove large snap ring, located in front of rotary valve shaft seal.

Wrap rotary valve in cloth and store in safe place.

Rotary valve shaft replacement-Water pump housing & impeller removal

Tools Required
10 mm socket
screw driver


Located directly below the exhaust manifold is the water pump housing, it is retained by 4, 10 mm socket head self threading bolts, remove these and the housing can be removed.

This will expose the water pump impeller and retaining nut. Remove the 10 mm nut, and flat washer. Remove the impeller, remove the special serrated washer and flat washer.


It may be necessary to gently tap the housing with a plastic hammer to break it free from the sealing gasket.


New water pump impellers come with a 4 mm hole drilled in them to help prevent air pockets, and overheating.


New water pump housings have two drain holes, located top and bottom for better bleeding of the cooling system.


It is sometimes necessary to apply pressure to the sides of the water pump impeller to break it free from the shaft.

Rotary valve shaft replacement-Shaft removal.

Tools Required
extrusion jig (876 612)

Shaft removal.

..Insert the extrusion jig (part # 876 612) onto the water pump end of the rotary valve shaft, threading it in until it is butts against the end of the shaft. Using a propane torch heat the rotary valve side of engine. Carefully, and forcefully strike the end of the jig with a hammer. This will drive the rotary valve shaft out the intake side of the crankcases.


Use extreme Caution when hitting shaft. Make sure the driving force is straight down onto the shaft end, or damage to the shaft will result.

Screw extrusion jig 876 612 onto end of rotary valve shaft, thread it on until it butts end of shaft.

Rotary valve shaft replacement-Shaft Disassembly

.Tools Required.
small screw driver
extrusion jig
half of bearing puller tool


Pressing the gear end of the rotary valve shaft against your body, with your fingers apply pressure down on the spring holding cup (2), break the circlip (1) free from its retaining groove on the rotary valve shaft. This will allow removal of the spring (3) gear (4) O ring (5) and shim (6).
To remove bearing, spacer and shim, install the lower half of a bearing puller in behind the bearing, supporting the bearing and shaft carefully hit the end of the extrusion jig protecting the other end of the shaft.

Another Procedure that can be used is a small press. Support the bearing, then gently press down on the jig protected end of the shaft until the bearing, spacer and shim come free.

Reassembly -Rotary valve shaft

Tools Required
extrusion jig
hot plate
oil container

Shop supplies
Loctite 648/271
grease Parts
Rotary valve oil seal
O ring
Compression spring


Apply grease to lubricate the lips of the rotary valve seal. Then install the seal onto the shaft. Heat a small quantity of your two stroke engine oil to 200 degrees F. Submerge the rotary valve shaft bearing in the oil for approximately 5 minutes. Install small quantity of Loctite 648/271 onto shaft where bearing will ride. Using gloves remove the bearing from the oil and install it on the shaft until it rests against end of shaft cut out. Install shim. Apply a small quantity of Loctite 648/271 green to the shaft area immediately in front of the shim, install spacer. Rotate the spacer to distribute the Loctite evenly. Install shim. Install rubber O ring. Install gear. Install spring. Install spring holding cup. Using spring holding cup compress spring. Install circlip, make sure that it seats properly.

Rotary valve shaft 937 969 (with oil injection)
Rotary valve shaft 937 962 (without oil injection)
Rotary valve seal 850 710
Rotary valve gear 935 730
Rotary valve spring 938 810
Rotary valve circlip 845 160
Water pump housing gasket

831 616

Reassembly-Rotary valve shaft installation.

Tools Required
circlip pliers
rotary valve shaft guide sleeve (876 612)
Rotary valve oil seal and support shaft insertion jig (876 602)
outer seal insertion jig (877 050)
inner seal insertion jig (876 512)

Parts required
2 seals
1 rubber washer
1 spacer
1 supporting plate.

Shop supplies
Molykote 111 silicone grease


Lubricate the inside of the inner seal with Molykote 111, and using inner seal insertion jig (876 512), insert the inner seal. Insert the spacer ring making sure that the opening in the ring is facing the weeper hole. Lubricate the outer seal then using seal insertion jig (877 050), insert seal into shaft cavity.

Install spacer, rubber washer and supporting plate, use insertion jig to install supporting plate.

Reassembly-Rotary valve shaft installation.


Place rotary valve shaft assembly in freezer for approximately 15 minutes prior to installation, remove and place rotary valve shaft, with guide sleeve on end into rotary valve hole, intake side, until bearing rests against crankcase halves. Cover shaft gear with insertion jig 876 602, Use a propane torch to heat rotary valve side of engine, then using hammer, sharply strike tool, until shaft is installed. Install circlip, making sure sharp edge of circlip is facing out.

Install flat washer, serrated washer, water pump impeller, flat washer, apply Loctite 242 then install locking nut. Install gasket, install housing, place blue loctite on self threading bolts, install the four self threading bolts. For proper torque specifications refer to section N. For rotary valve timing refer to

Section K Rotary valve timing.


Install seals facing direction shown in Fig 80A.

Note if shaft has been damage by the seals REVERSE the seals on the shaft after cleaning it and you can STILL use the shaft.

Install Molykote 111 into seal cavities in areas shown, in Fig 80A.


Ensure circlip is properly seated into groove in crankcase half.


Check locknut to make sure lock is still working. If suspect replace.


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