Great video, there is a torque bolt pattern for this engine and it is not a zig zag. Both heads are considered one unit by Rotax. The torque pattern can be found on page 40 of the Maintenance Manual.
ya, go work in a shop with some real mechanics for a while. Their method is silly, just use some 400 W/D with a bit of motor oil, do small sections at a time and wipe it off quickly with a rag, no junk falls into the motor that way.
How about using modern fuel and synthetic 2 stroke oil ? I dont have an aircraft engine but with the 2 stroke engines that I use I never decarbed any engine and when I take them appart there is nothing to clean out.
you can just push the ring into the cylinder with your fingers, you don't need to use hose clamps...sheesh. anyway, it's much easier to just use some 400 wet dry sand paper and a bit of motor oil, gently swirl the sand paper on the carbon with some oil (a bit at a time) and then wipe it off with a rag, this way you don't have to worry about any carbon coming off and flying around in the engine.
Hey, I'm a rookie "503 maintainer", but: That looked like a chineese fire drill to me! Agree on the "bashing" of the ratchet - use a breaker bar! Did it need decarboned? Naw. Just an exercise in futility.
I am afraid I’m going to have to disagree on recommending this video. There are several things wrong with it. Some of the things wrong is that it appears from the video that they didn’t remove the pistons from the engine. They should have been removed to inspect the wrist pin and bearings and to isolate the carbon removal from the engine itself. They way they cleaned the top of the piston is surely going to allow carbon particles to get into the crankcase even though they put some rags around the top of the crankcase. These hard bits of carbon, even though tiny, are going to eventually run through the crank bearings and the piston and rings. Also in the video, he recommended removing carbon from the sides of the ring. This has to be done but it is not enough. The main problem with carbon and cylinder rings on a two stroke is carbon build up on the back side of the rings and a corresponding carbon buildup in the ring grooves. When enough carbon builds up here, it prevents the ring from retracting slightly into the ring groove to accommodate the differences in temp of the cylinder, ring and piston. The piston ring has a bit of ‘spring’ to it. This spring tension holds the piston ring against the cylinder wall with the correct amount of tension to ensure sealing but no so much that the oil coating cannot lubricate the ring and cylinder wall to prevent excessive friction. When carbon buildup on the ring and down in the ring groove build up enough, the ring becomes locked in the ring grove and when the piston expands more than the cylinder, the ring is then forced to exert excessive pressure against the cylinder wall which causes excess friction and results in a seizure. Another big problem is the improper use of piston blocking on the bottom to hold the piston in place while the cylinders are being replaced on the pistons assemblies. They apparently cut pieces from plywood for this. Plywood is OK but the slots cut into them should fit over the connecting rod and not the head stud. One block cut generally like they cut theirs to fit the bottom of the pistons, slotted for the rod, narrow enough to fit between the head studs and long enough to fit all the way across the crankcase would have been correct. In this manner, the piston assembly is held up for installation of the cylinder and it is held securely parallel to the path the cylinder will have to be slid down over the piston. Cocked sideways by two blocks that don’t fit will not hold the piston ‘square’. One of the biggest problems is the use of hose clamps to compress the rings. This is almost surely going to result in a score mark being forced into the face of the rings and probably onto the piston also. It can also very easily result in a broken ring. The bottom of the cylinder is tapered for the purpose of allowing the cylinder to fit over the piston assembly with only finger pressure to compress the ring. The piston rings in a two stroke are pinned into the correct orientation on the piston. This is necessary due to piston porting on a two stroke engine. If the ring is not held in the exact correct orientation on this pin that is in the ring groove of the piston and if you were to try and force the ring down into the groove, the ring will break. The correct procedure is to oil the cylinder and piston along with oiling the rings themselves and the ring grooves. Next, block the piston securely and square to the crankcase (the reason for the correct tool, even a home made one), orient the top ring to the pin and compress it with your fingers. Then slowly lower the cylinder down onto the top of the piston. With your fingers and the cylinder taper, let the top ring slide up into the cylinder. This will take a bit of light manipulation (never use much force here) with your fingers but when everything is in the right place and orientation, the cylinder will drop down over the ring with only a slight bump by hand on top of the cylinder. Repeat for the second ring. One more thing that bothers me is the use of sealant on manifold gaskets, these should only be coated with a light coat of oil and installed. This video has been around for a very long time and it just has so much wrong with it that I am surprised that it is still up. George
