Checking the level of fork oil on a Honda XL250 requires draining the oil and refilling with the correct amount. A good indication of a low oil condition is soft front suspension damping or bottoming out on rough terrain. An easy way to test the fork damping ability is to tap the front brake at 10 miles per hour several times. Pay attention to the amount of dive in the front and how fast it recovers. If there is excess dive and slow recovery, the fork oil needs to be checked.
Raise the motorcycle enough to allow the front forks to extend fully. Remove the top fork tube cap nut, keeping in mind the forks are spring-loaded and even with the forks extended, there will still be some compression. Do one fork at a time.
Remove the lower fork tube drain plug. Allow the oil to drain completely. Install the drain plug and tighten it with a wrench.
Fill the fork tube through the top with 145cc of 7-15 weight transmission fluid. Install the top fork tube cap and tighten securely with a wrench. Do the same procedure to the opposite side.