Please follow these instructions carefully
With a sharp instrument mark the front of the cooling fins and cylinder unit so that these two components can be replaced exactly as found.
Now remove the holding-down screws, and the cooling fins. 249/19 DS and earlier models only:- Cut off lowest 2 fins and file small flat to clear silencer box on next fin if necessary. 149 DS and earlier, remove ONE FIN ONLY. 049/06 no fins need to be removed.
Place the first sealing ring over the cylinder unit on to the case: follow this by the silencer, trying to get the screw holes in the correct position for assembly. The top sealing ring is now placed on the silencer ring, and is followed by the cooling fins.
Holding the engine in your left hand, with your left thumb on top of the cooling fins, take a needle and probe down the screw holes to make a SMALL HOLE in both sealing rings in each of the three screw holes. DO NOT make this a large hole, or you will lose gas (and noise) past the screws.
IT IS IMPORTANT that the sealing washers are trapped and held in their correct position when the holes are pierced.
You can now screw in the holding-down screws using a sharp screwdriver, and taking the greatest care to note that the cylinder unit is still correctly positioned, and trapped, as it was when the engine was dismantled.
If you feel that you have reason to believe that your cylinder unit is not correctly held, please send the engine and the complete silencer set direct to:-
PROGRESS AERO WORKS, Union Street, Macclesfield with a fitting charge of £18 when the silencer will be correctly fitted to your engine and returned with despatch.