Part 27 Refitting The Cylinder Barrels ...

Introduction ...

This page contains photos of the process of refitting the cylinder barrels to a ROTAX 912ULS engine (built August 2006).



ROTAX 912ULS refitting the cylinder barrels

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Here is the cylinder barrel back from the cleaning process ...

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ROTAX 912ULS refitting the cylinder barrels

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Note that the crosshatching is in good shape and any carbon deposits have been removed. Take this opportunity to thourougly clean the inside of the barrel and apply some engine oil to the Nikasil coating. Here I am using an old 3 in 1 oil can which is filled with AeroShell engine oil to apply a coat of oil to the inside of the barrel ...

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ROTAX 912ULS refitting the cylinder barrels

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Place a new cylinder base o-ring into it's locating groove at the base of the cylinder and generously apply engine oil ..

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ROTAX 912ULS refitting the cylinder barrels

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Offer up the barrel to the piston and very carefully slide the barrel over the piston. Unfortunatly it is very hard to photograph the piston ring compression tool in use as the is a two handed job and it is challenging to hold a camera to hold it whilst you are doing this ...

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ROTAX 912ULS refitting the cylinder barrels

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Here is the barrel started on the piston and all piston rings are now safely compressed and inside the barrel. The orientation of the piston rings is very important. The gap in the oil scavenging ring should face downwards and the two upper compression rings face out either side of the vertical. Please reference the current version of the Heavy Maintenance Manual for a clearer idea and more info on the exact orientation of the piston rings ...

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ROTAX 912ULS refitting the cylinder barrels

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This is a view inside the barrel showing the crown of the piston. Note here that the line that demarcates the limit of travel of the piston has had all carbon deposites removed above it. Note again the orientation of the arrow on the piston crown ...

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ROTAX 912ULS refitting the cylinder barrels

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Gently push to barrel home over the piston until it is fully seated on the crankcase ...

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ROTAX 912ULS refitting the cylinder barrels

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Once the barrel is fully home refit the upper studs. At this point it is a good idea to refit teporarily the cylinder head minus pushrod tubes. This will hold the barrel captive and stop it from moving when you turn the crankshaft in order to position the conrod for the next cylinder barrel. You only ready need to finger tighten a couple of the cylinder heads nuts. This will suffice ...

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ROTAX 912ULS refitting the cylinder barrels

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And on to cylinder 2 ...

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ROTAX 912ULS refitting the cylinder barrels

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Note that once the piston rings are all started in the barrel then the piston ring compression tool can be routed around the conrod and allowed to drop onto the bench below the barrel ...

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ROTAX 912ULS refitting the cylinder barrels

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Here we can see the cylinder barrels 1 and 2 in place, and temporarily retained in place by their respective cylinder heads ...

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ROTAX 912ULS refitting the cylinder barrels

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Cylinder 3 barrel in place ...

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ROTAX 912ULS refitting the cylinder barrels

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Finally all four barrels in place ...

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ROTAX 912ULS refitting the cylinder barrels

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And a plan view of the build so far ...

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