How to and what not to do... I have found there are several things to watch out for. First of all, jack up the plane so the weel extends all the way down. Push the wheel up and down to feel the current hydraulic damping. If it is good, your sysyem is working and may just need topping off. If it is not you will feel it when pushing the wheel up. First thing to check is the bumpers. these are little rubber stops on the landing gear leg and on the strut. When the wheel drops down, the motion is stopped by a rubber bumper that is attached to this little arm. If it is missing, which is quite common, you are in trouble. The wheel has been dropping too far down, the filler hole has a rough edge on the inside of the cylinder and it destroys the seal. if you have a seal cup version. If you have the O'ring version, you need to take it off and get a seal cup kit from Skyport. The O'ring version was made to last 10 years at best and none will last long. It was a great idea at the time but there is better now. When you take the cylinder apart, you will see if you have the cup or the O'ring. You can leave the O'ring on as it will not harm anything. You will have to wash out the cylinder which is made of steel and probably has rust on the inside. Go to the auto parts store and buy a small 3 blade fine ctlinder hone that will fit inside. ( take the cylinder with you to test if it fits or make a second trip). You then hone out the inside surface with this device in a power drill and with diesel or kerosene in the cylinder. If you don't do this, the rust will eat up your cup seal. Wash it out well. Clean up the piston surface with sandpaper and diesel or with a wire wheel brush and install the cup kit as instructed. I find it is easier to fill the cylinder before installing it on the plane. Just pour the fluid into the cylinder and inser the piston seal and slowly push it down. Any excess fluid will come out the fill hole. inser the plug into the fill hole and safety wire. Put it on the plane and test the damping motion. If you need to top off the fluid, remove the rubber bumper and inspect it. Drop the wheel as low as it will go and add fluid through the filler hole. I use that syringe the dentist gave me to irrigate my wisdom tooth hole. An old oil can also works. The U cup seal is now above the filler hole. Do not push the wheel up now. Fill with fluid until it runs over and then push a wooden chopstick into the hole to carefully help the cup lip over the filler hole inside surface while slowly pushing the wheel up. Once the U cup seal is below the filler hole, prop the wheel up so it does not drop again and re-install the filler plug with safety wire and re-install rubber bumper. With the rubber bumper installed, you can now drop the wheel all the way down again and the U cup seal will remain below the filler hole. Now test the damping.
