DIY Fork Oil Change
by Mike Blair & Walt Cloudt
The manual specifies a fork oil change every 20,000 miles or every year. Hereís how to do it yourself! The instructions assume youíve got a shop manual, but itís not difficult even if you donít. Mike and I did this about the same time (Mike in Canada, Walt in Virginia), so where we differed on method, itís noted. Fluid viscosity and level can be used to tailor the suspension action. We donít go into that here. Specified fluid level is used, although we did use different viscosities.
We proceeded as the book shows but without their special tools and it went very well.
Flushing the forks is optional. After Mike drained the old oil, some fresh regular Dexron was pumped through a few cycles to flush out the innerds.
Here are some notes about the job before we begin :
Lay out everything you are going to use beforehand. Itís a bugger to go get something when your hands are dripping with oil. Plan a place to hang the forks upside down over a pan to let them drip. Have lots of newspaper and rags on hand.
The nut under the top plug is 14mm.
Once the plug, washers and spacer are off, before you let go of the piston rod, slip a length of 3/8 id hose (8 inches of clear plastic gas line works well) over the end of the rod. This will allow you to pump the rod later. Donít worry if the rod slips down into the tube, itís easy to fish up with a finger.
While the forks are off, itís a good time to slide the dust seal off and make sure that there is no grit trapped under it.
When the springs are lifted out they drip lots of oil so be ready with the rags.
Check the length of the springs against spec before they are put back.
Mike used 100% synthetic Dexron III. Walt used 15W Yamaha shock oil. There are lots to choose from. Viscosities between 10W and 20W are recommended by Kawasaki. Viscosity selection can be used to tailor the suspension action.
A dipstick should work to measure the fluid level (124mm from the top) if you fill the tube carefully. You could use a length of clear gas line as a pipette to remove some oil if you have to. Fluid level can be used to tailor the suspension action. We wonít get into that here.
It is so much better to make a suction tool using a plastic syringe. Mikeís came from a veterinarian (50ml size). Walmart sells a translucent plastic syringe called a MixMizer ($3 US) for measuring 2 stroke oil doses that worked great for Walt. With some tubing provided with it, slipped over the spigot and cut to 124 mm (4-7/8Ē) from the shoulder it works just as well as the tool shown in the manual. Besides the fork job, it is excellent for sucking out master cylinders when changing brake fluid.
Okay, youíve got all your tools laid out, plenty of rags, etc. Here we go....
1. Support the bike so the front wheel is off the ground a couple inches. Walt used a ratchet hoist attached to the handle bars. You can also jack up the bike with a floor jack and support the frame below the engine on blocks. Mike used a special front end support he made. Itís pretty slick!
2. Remove the front wheel, brakes and fender. Note: Youíll need a 17mm or 22mm hex wrench to loosen the front axle nut.
3. Loosen the top triple clamp bolts.
4. Loosen the top fork end caps. A 1-1/16Ē wrench works if you donít have a metric this big!
5. Loosen the lower triple clamp bolts.
6. Slide the fork tubes out of the triple clamps.
7. Using and 17mm wrench loosen the spring preload adjusters completely.
8. Hold the forks upright for the remaining steps (unless you like oil everywhere) and proceed to unscrew the end caps from the upper fork turbes completely.
9. Use a 14mm wrench to hold the nut under the end cap, and turn the end cap using the spring preload adjustment with a 17mm wrench until the end cap breaks loose, then turn if off by hand.
10. Remove the loose parts. Youíll have 2 flat washers, a spacer and a small tube sticking up from inside the piston rod from each leg. Place all these on rags as theyíll be dripping some oil. Finally remove the springs. These will drip a lot of oil!
11. Slip a piece of 3/8Ē i.d. tubing over the end of the piston rod. If the rod has slipped down inside the upper fork tube, push the upper fork tube down into the fork leg, to the end of itís travel, fish the rod out and then slip on the tubing.
12. Hang the forktubes inverted over a drain pan. Using the 3/8Ē tubing, pump the piston rod back and forth to the ends of itís travel at least 10 times. Leave the forks hanging and allow to drain into your catch pan. Flush out the forks if you wish at this point.
13. Hold the forktube upright for the remaining steps. Push the upper fork tube and the inner rod down as far as they will go. Pour fork oil into the tube until itís roughly 5Ē from the top. Pump the piston rod at least 10 times. Allow any trapped air bubbles to escape the oil. Finally add or remove oil until itís 124mm from the top. Use the a syringe or pipette or MixMizer or whatever to remove any excess, so that youíre within plus or minus 2 mm of 124mm to the top.
14. Set the rebound adjustment of the end cap to 25mm from the lower shoulder to the adjustment screw. Reassemble the fork tubes in reverse order of how they came apart. Reset the spring preload back to where it was (itís easier to do it now). Reset the rebound adjustment to where it was too.
15. Insert the fork tubes into the triple clamps so the top of the upper tube is even with the top of the upper triple clamp. Torque the triple clamp bolts to specs. Install the front fender, wheel, brakes and torque all the remaining bolts to specs.
16. Take a test ride and enjoy. Park the bike, grab a beer and pat yourself on the back. Good Job!