How much fork oil do you use on a 1990 kx 250?

Answer 1

AT YOUR OWN RISK: I have two 1990 KX125's. They use the same forks (41mm KYB's) as the 1990 KX250 except with softer internal springs and probably a softer shim stack. Anyway, the fork oil level is actually a suspension setting. The more oil that you put in (within correct range), the stiffer the damping will be and less oil is softer. But, for the typical oil change each fork will use 12.7 ounces (per manual). 15 oz for complete disassembly (e.g. re-valve). You will want to set the oil level at about 100mm from the top of the upper fork tube after the forks are resealed and completely assembled with the top cap off and the fork completely compressed. It takes no effort to compress them as the springs are sticking out of the top. You should avoid varying the oil level more than 70mm (Min.) and 120mm (Max.). The easiest way to set the oil level is to get a syringe for dosing babies and attach a straw cut to 100mm (or your preferred level). Fill the fork to a little higher than the desired level and draw out the excess oil with the straw/syringe setup. Make sure to get the straw even with the top of the upper fork tube and between the inner wall of the upper tube and internal spring. You will also want to purge the air from the forks by pumping the small pushrod up/down ~5 times then the upper fork tube up/down. Set the fork aside for 5 mins to let any air bubbles rise. Then check oil level for final time. Probably too much info, but just wanted to keep it safe.