fork oil replacement and overhaul tips

It is best to dismantle the forks if you are planning to do a fork oil change on your bike. There are forks with drain plugs found at the bottom and some people will just drain the oil over night and measure the amount of oil that came out and add the same amount of new fork oil to the fork. Some people will not even dismantle the forks from their bikes when they do this kind of oil change. 

Normal and inverted forks are basically the same. To do a full and proper fork oil change is to: dismantle the forks but it will help if you loosen up the uppermost bolts that holds the fork from the top bridge and loosen up the the big nut found at the end of the inner tube. There are some inverted forks that have holders and you have to clamp it on a vise to open the nut at the end. The nut found at the end of the inner tube is where you pour in the oil. Remember that there are some forks fitted with adjusters found on the center. Most are dial types and some even have the air pump valve. You must first know what type of forks your bike has. Most forks have the spring and the damper found in one unit and there are times that a small valve is fitted between the end cap (nut found at the end of the inner tube) and the damping rod inside the fork. There is a double nut that locks the damping rod from the end cap and be VERY careful not to loose the small valve found in between the two. 2nd pull out the spring and dump the oil. Pump the inner tube until all the oil comes out. Take off the dust seal, oil seal spring lock, oil seal and pull the inner tube out from the outer tube. You have to pull it out several times until the two has been disconnected. Loosen the the big bolt found at the end of the endpipe so that you can pull out the damping unit. Pump the damping until there is no oil left. Some damping must be pumped many times to get all the oil out. Clean all the parts. Replace all the damping unit's rubber. Assemble the fork and put in new oil seal. Clamp the fork and level it 90 deg. Fully extend the inner tube and pour in the fork fluid. Connect the damping rod to the end cap. FINISH!
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EASY way to do a full oil change: Do everything that I wrote but do not dismantle the dust cap, oil seal and the inner tube from the outer tube. Just dump the oil out from the tube. Invert the tube and retract the inner tube to full. hold the damping rod and pump it until all the oil has come out. There are some models that will take you several minutes of pumping to get all the oil out from the damping unit. (my bike take at least 10 mins until I can get all the oil out from the damping unit) TAKE YOUR TIME. You will know that all the oil has been dumpted out by standing the fork upright and releasing the damping rod and if it falls straight to the bottom, then all the oil has been dumpted and if not... just keep on pumping again. Put new fork fluid, close the end cap... FINISH!

REMEMBER: You must know the proper fork fluid and the proper amount of oil for your fork. Always measure the amount of oil from a graduated mess cylinder. Always pour in the oil with the inner tube in extended position. Always pump the damping rod to let oil inside the damping unit and get the air out. Put oil or silicone grease on the oring at the end cap before installation. You can also use a measuring stick if you dont have a graduated cylinder or you have not fully dumpted all the old oil inside the damping unit. 

USEFUL HOME MADE MEASURING TOOL FOR FORK OIL MEASUREMENT. You need syringe but you dont need the needle, a small hose that fits the end of the syringe, a measuring stick or a pre measured rod (anything will do just put a marking) this will be your scale. Pour the oil inside the tube and suck the excess oil out using the syringe. 

*** Techies wont like this... I use specified fork fluid but if I ran out of stock, I use Toyota Dextron 2 ATF (automatic transmission fluid) but I find it too hard but works well for some bikes. I change my fork fluid every 3 months and sometimes I ran out of stock (oil) so I use ATF (I have cans of ATF at stock everytime...) Many MX, trials, and some road racers also use ATF. It's up to you... Many trials use no.5 or no.10 fork fluid but I prefer a more softer oil. The best is to follow what your manual says and you will never be wrong.