The Rotax starter can exhibit all manner of small problems making starting the engine difficult an frustrating. This text will hopefully allow you to fix this situation with easier and faster stating.
First, remove the starter from the engine. Some will use hex bolts and other will use allen head screws. In either case, removing the fan housing will make starter removal possible.
Start by removing the small snap ring and the pullback spring. It is strongle suggested that they be layed exactly like they are removed, as far as the circular orientation. This will make re-assembly much easier.
A small screwdriver may remove the larger snap ring, and then the two plastic pieces.
The rope should now be pulled to its full extent and the small pawl be removed, making sure to hold the large pulley. Then allow the pulley to slowly unwind. make sure the pulley is in a neutral position, and then lift it free of the starter housing. Carefully remove the spring cup out of the housing, and VERY carefully remove the spring. Wear gloves for protection, and allow it to unwind. It will be like a big sloppy spring, and should be held carefully so as to not kink it.
A the parts should be cleaned as dirt wears the parts prematurely, and also causes the pulley to drag, the spring to drag, making starter operation sluggish.
The rope will be replaced and a special type knot is used. The loose end goes through twice. To keep the rope clean, every piece touched will need to be meticulously cleaned. Thread the rope and replace the rubber bumper. To prepare the rope for further threading in the winding pulley, heat the end with a small propane torch, and wipe it with a folded piece of cardboard. This will firm the end a bit and also taper it.
Hold the starter spring cup with the open side towards you, place the rolled outer end of the spring inside with the end in the small slot. Wrap the spring clockwise and carefully hold it with your thumbs and spiral the entire spring into the spring cup. Place the cup with the open spring side facing down into the starter housing. The small loop end should be about 1/8 inch from the central pin of the housing. This will allow easy assembly of the large pulley.
Check the back of the large rope pulley and note that the end of the spring must fit the small opening in the center rim. The pulley is designed to operate either left or right hand, but if the spring was wrapped propely, just place the pulley into the housing making sure the spring engages the pulley notch. The pulley should be able to be wound now, and as the rope will be inserted from the lower left, the pulley needs to be wound fully counterclockwise towards the rope opening.
Important,,,,,,,,,to assure that the rope does NOT pull the pulley such that the spring bottoms out, thus breaking the spring, wind the pulley/spring until it is tight in the COUNTER clockwise direction. Then back the pulley off until the rope slot aligns with the hole in the starter housing. Stick the rope in the hole and insert the small rope pawl.
Install the two plastic parts and the large snap ring. Use pliers as shown.
Install the spring and pop the small snap ring on the end of the pulley shaft. The starter should work freely and retract fully. If you care to, pull the rope completely out of the starter , and check that the pulley can be rotated a bit more assuring the safe operation regarding the large return spring.
One last item. Rotax supplied two different ropes,,,, a short one for quicksilvers where the handle retracts all the way to the starter housing,,,,,,,, and a longer rope for those cases where the handle is stopped prior to touching the housing. The rope pulley will only hold so much rope, so trying to install the long rope may cause the last wind of rope to rub the inside of the housing. This causes a sluggish retraction possibly not pulling all the rope in. Also, the spring can only pull so much rope before running out of steam worsening this problem. Try to keep the active rope being wound to 4 feet or so. If you think having more rope will start the engine, you might want to rebuild the engine,,,,,,,,,