| This
issue I’ll give you a quick run down on how to change
your own fork oil. We’ll stick to KYB bumper style
forks. Yamaha and some other late model MX’ers use
these forks so check your owner’s manual before getting
started.
It’s probably best
that you have some kind of mechanical capabilities before
attempting this kind of task, if not I suggest taking your
suspension to a professional.
The first thing you’ll
want to do is wash your bike. Next put it on a sturdy center
stand (one that’s not going to tip over when the
forks are off).
You’ll need to remove
the front wheel (for obvious reasons!!!). When
you get the wheel off, it’s best to take the brake
caliper and fork guards off at the same time for convenience
sake. The forks should slide out pretty easy if the bike
is fairly new, if they don’t you can GENTLY pry the
triple clamps apart with a small flat screwdriver and they
should slip out (be sure to hold the bottom of the fork
so it doesn’t smash the ground).
With your forks off, make
sure they are clean and dry then we can get down to business.
It’s a good idea to use a soft jaw vice so you don’t
mark up the bottom of the forks and use some kind of bucket
or tray to drain the fork oil into.
Step One:
Undo the cap from the outer tube, slide the tube down and
turn the fork upside down to drain for a while.
Step Two:
Remove the fork cap from the piston rod (see photo below).
You’ll need a 17mm wrench to hold the lock nut under
the cap. Then pull the spring and rebound adjuster rod out
and wipe with a CLEAN RAG.
Step
2 Photo Step Three:
With the bottom of the fork tube securely fastened in the
vice, pull the piston rod out of the fork and keep pulling
(see photo below). With a 14mm allen socket and
an air impact gun, undo the bottom adjuster bolt and the
cartridge should slide out of the fork tube. Be careful
when removing the cartridge, there is a lot of oil inside
and it’ll spill everywhere. Then dump the remaining
oil from the tube into the pan. The easiest way to get the
compression adjuster out of the tube is to use a CLEAN wooden
dowel and gently tap it.
Step
3 Photo
Step Four:
The next step is probably one of the most important. I can’t
stress enough how important cleanliness is when dealing
with suspension components. You can use either contact cleaner
or a solvent tank depending on your resources to clean the
inner tubes and cartridge of old oil and debris. The best
way to do a final clean up is with compressed air. Blow
off all internals and set to dry for a bit.
Step Five:
Re-assembly. When the parts are clean and dry, place the
outer tube back into the vice. Insert the cartridge into
the tube and gently hand tighten the compression adjuster
into the fork. Keep in mind the threads are aluminum so
be certain not to cross-thread or it could get expensive!!
With the adjuster hand tight, torque it down to 40 ft.lbs.
Step Six:
Stand the tube upright, insert the rebound adjuster rod
and fill with fork oil (see photo below). Generally
5wt oil is required but check your owner’s manual
for specifics. Once the fork is filled, bleed the cartridge
by stroking the piston rod up and down until it is filled
with oil. You’ll need to add oil as the level drops
so keep the bottle handy. The best thing to do is leave
the forks sit for a while to let the rest of the air bleed
out.
Step
6 Photo
Step Seven:
It’s important to leave the spring out until after
the oil level has been set. Depending on the application
and rider preference the oil height will vary (see photo
below). I would suggest setting it between 90mm and
115mm depending upon how stiff or soft you like your forks
(90mm being stiffer and 115mm softer). After setting
the height pull up and down on the outer tube and then reset
level. With that done, pull up on the rod and install the
spring. Before installing the cap, back off the rebound
adjuster screw so it doesn’t crush the rod. Torque
the cap to 15ft.lbs. and tighten the cap onto the outer
tube.
Step
7 Photo
Step Eight:
Reset the rebound adjuster to its original setting and install
the forks back onto your bike. Make sure that the air bleed
screws are facing forward so you can get at them later without
removing the handlebars. Torque the pinch bolts to 14 and
12 ft.lbs. (top and bottom). Also be sure to center
the axle before tightening the right side pinch bolts or
the forks will bind and feel harsh.
These steps should be
pretty easy to follow so good luck and if there are any
problems or questions you can always email me at stu@machineracing.com.
‘Till
next time, see you at the races!
Adam |
