Your ZRX 1100s front fork is a fairly durable item that can withstand a great deal of abuse. However, its fork seals, which prevent the fork fluid from leaking, are easily damaged. Replacing your ZRX 1100s fork seals doesn't have to be an expensive proposition. If fact, armed with some basic hand tools and a decent motorcycle service stand, you can replace the fork seals yourself with a little bit of elbow work. The front wheel, brakes and fender will need to be removed first, so plan to spend a minimum of two hours to complete this job.
Loosen the pinch bolts on the bottom of the lower fork sliders with a 12mm socket and a socket wrench. Loosen the front axle nut with a 17mm Allen wrench. Loosen the front brake caliper mounting bolts with a 14mm socket. Place your ZRX 1100 on a service stand and lift the front wheel off the floor.
Unscrew the brake caliper mounting bolts from the lower fork sliders, using a 14mm socket. Lift the calipers off the front wheel's brake rotors. Unscrew the front axle nut with a 17mm Allen wrench, then pull the axle out of the front fork and wheel. Remove the front fender from the lower fork sliders, using a 4mm Allen wrench
Loosen the cap on the top of both fork legs, extending above the upper triple clamp, using a 22mm socket. Loosen the pinch bolts on the sides of the upper and lower triple clamps, using a 12mm socket. Pull the fork legs out from the bottom of the triple clamps, using a twisting motion.
Turn the spring pre-load adjuster -- the hexagonal adjuster positioned on the top of the fork cap -- counterclockwise with a 12mm wrench until it cannot turn. Unscrew the top caps from the fork tubes with a 22mm socket. Pull the cap up and pull the piston rod, attached to the bottom of the cap, out of the fork tube. Unscrew the cap from the piston rod with a 12mm wrench, while holding the nut on the top of the piston rod with another 12mm wrench.
Pull the washer, spacer and spring out of the top of the fork tube. Pour the fork's fluid into a container. Pump the fork tube repeatedly to ensure a complete drain.
Unscrew the bolt from the bottom of the fork leg with a 6mm Allen wrench to free the piston rod. Pull the piston rod out of the fork leg. Pull the rubber boot off the fork's lower slider to reveal the fork seal and its C-clip. Remove the C-clip with a flat screwdriver. Push the fork tube into the slider, then pull the tube forcefully against the fork seal. Repeat until the seal pops out of the lower slider, then slip the fork seal off the top of the fork tube.
Lubricate a new fork seal with fresh SAE 10W fork fluid, then slide it down the fork tube. Insert the fork tube into the lower slider, placing the fork seal along the top of the slider. Set the fork seal into place with a seal driver. Slip the C-clip into the groove cut into the top of the lower slider. Slide the rubber boot down the fork tube and press it into place over the lower slider.
Reinsert the piston rod into the fork tube. Screw the bolt into the bottom of the lower slider with a 6mm Allen wrench to hold the piston rod in place. Push the fork tube into the slider and pour up to 473ml of SAE 10W fork fluid into the tube. Stroke the tube up and down to distribute the fork fluid.
Re-insert the fork spring, spacer and washer into the fork tube. Screw the top cap onto the piston rod, using a 12mm wrench. Re-install the fork leg onto your ZRX. Replace the remaining fork's seal, using the same method.
Re-install the front wheel, brake calipers and fender, following the reverse method of removal.
Kawasaki offers a service manual, filled with detailed maintenance and repair instructions, that could be beneficial to this task. These manuals may be purchased from your local Kawasaki dealer.
Fork seals are easily damaged by rust or debris on the surface of the fork tubes. Look at the condition of the fork tubes before installing the fork seals. If the tubes are damaged or rusted, replace the fork tubes before continuing.