|Written by Eric Harnish
It is always nice to see an inquisitive
mind. Lets see if I can help you out and the few others who ask
why. I'm going to write this with the do it your selfer in mind.
We have covered in depth as to the why a high or low speed wobble
occurs. In a nut shell 90 % of the wobbles are caused by bad or
poorly adjusted steering bearings. If you have a wobble and need
to test the bearings there is only one way.
That is to take the front end apart, clean up the bearings and races
and visually inspect them. The factory and what is written in a
lot of text test procedures are not definitive. They tell you to
jack up the front end and pull up and down on the forks to feel for
play. They also tell you to rotate the steering to feel for
notchyness. Well .... I will assure you that if you follow this
test procedure and feel play or rotational problems your bearings were
bad a long time ago. I lost count on how many times someone who
was looking for the cause of a wobble, they tell me the bearings were
good because they used these test procedures, believed the results, only
to face the problem, and found bad bearings after tear down. If
you have a wobble your bearings can be bad and pass the factory test
procedures. The only definitive way to verify that the bearings
are good or bad, if you have a wobble, is to take
the steering stem out and visually inspect the bearings.
The very slightest of movement or damage to the bearings can cause a
wobble and I have seen brand new bikes out of the box with bad bearings.
What you are looking for during an inspection is, with the races ,
vertical marks going up and down on the race, missing plating, pitting, dents, corrosion, etc or anything that is not a perfectly smooth and
shiny surface .
With the bearings rotate each roller and look for pits, bent cage,
corrosion, out of round roller which shows up as light and dark spots or
sections of the roller that appear to be a different in shade of color.
If you find any imperfection, no matter how slight, replace the
bearings and races as a unit. Just as a note ....... If you want or
need to test a ball bearing assembly you remove it and place it in a
vise. Gently squish or pinch the outer race of the bearing and
then rotate it. If you feel roughness the bearing is bad.
You have to load a ball bearing to test it. Needle bearings are
visually inspected like taper rollers.
Lets go through a set up procedure.
Tools....... You are going to need at least three different torque
wrenches to work on the front end. I prefer the beam type because
I can see the torque rise and it is easier to watch when doing retorques.
A clicker will work just fine.
Torque wrenches work best in about 80 % of their ranges.
The torques that we are going to use are 36 ft lbs &
80 ft lbs ... need 0-150 lb wrench 2.2 ft lbs need 0-120 or 150 inch lb
wrench foot pounds X 12 = inch pounds 14 - 17 ft lbs or so... need 0-300
inch pound wrench . This wrench is used on most of
the fasteners on the bike.
A Socket to turn the ring nut. You can buy one from Yamaha or
make one out of an old socket. Just notch the old socket to fit
two of the nut's notches.
A simple spring scale that measures in a low range of 0-20 lbs or
so. I will not cover bearing & race removal. Pack the
bearings just like you do with the bearings on a car . Do not add grease
inside the neck. A little on the shaft and races is all that is
needed. When installing races... clean up
the bore in the steering neck. Make sure that there are no burs on
the edges or raised metal from deep scratches caused during removal .
Very lightly grease the outside surface of the races and the bore. Do
not pound on the inner portion of the race where the rollers ride. If
you have access to a bearing race installation tool use it for I do
highly recommend them. You can use a socket or old race to get it
started . The main thing is to inspect that the race is fully seated and
there are no slivers of metal trapped at the race seat when you are
Next look at the ring nuts or the nuts that have the notches cut out
of them. You will notice that on one side the edge is rounded
off. This side goes down. OK slide in
the steering shaft into the neck, the top bearing, the big washer or
washer cover, and the fist nut with the rounded edge down. The
factory tells us that they want us to torque the first time to 36 ft
lbs. I have found that 20 ft lbs the first time is best then bring
it up to 36 ft lbs of torque. A little more torque is just fine. While
you are torqueing the nut rotate the shaft back and forth , lock to
lock. The reason for the 36 ft lbs is to center the bearings and
if there is any play in the races it will pull them up tight.
After you have reached 36 ft lbs walk away from the job for a few hours
or so then check the torque again. Keep rotating the shaft back
and forth. Check the torque for a third
time. When you get the same 36 lbs of torque on the wrench three
times with out movement of the nut then you are done with the first
torque . Always torque three times on all fasteners. Now we are
ready for the second torque of the factory 2.2 lbs. I use 2.5 or
2.5 X 12 = 30 inch pounds . I use 30 because it is easier to see on the
Back off the nut and retorque to 30 inch pounds . The movement is
done all at the same time . Back it off all the way and bring it right
back to 30 in lbs . Rotate the shaft and check it two more times.
The result should be a perfectly smooth rotation and absolutely no play
at all. If it is not then take it apart and find out why.
Now this is where we are going to use a spring scale. Spring
scales are used to give us a reference and not to set the load on the
bearing. Now if we all used the same scale in a shop, and we have
done the job a dozen times or so, then we could assign a reference pull,
but we do not have that situation do we? The reason we are going to take
a measurement is to let us know if something changes during the rest of
the assembly process that would change the bearing preload. Go ahead and
slide in the forks. Install the fork brace with the bolts just snugged
up to help square the forks up. The height setting of the forks is
not important at this time. Just do a best guess. Just snug
up the lower triple clamp pinch bolts just barely tight enough to keep
the forks from slipping down. Take a tie wrap or whatever and wrap
it around one of the fork sliders. With the front end
centered, hook the spring scale to the wrap
and pull straight ahead slowly and gently until the fork moves Do it a
couple of times and then record the reading. Lets say it is 6
lbs. Now we are ready to install the second
ring nut. This is where a lot of confusion seams to be. Do
we install it as factory with the rubber washer and lock , or jam the
nuts on top of one another, or install a solid washer in between? All
three methods will work just fine if you understand what the final
result should be. Take a look at the top of the steering shaft.
You will see that it is tapered. This tapered shaft fits into the
tapered hole in the top triple clamp and the factory tells us to torque
the top or large retaining nut to 80 ft lbs. The call for 80 ft
lbs of torque is due to the taper fit and we do not want any movement in
the upper triple clamp. What we do not want is the top triple
touching the second nut on the shaft. If this happens then the
nuts will be forced or flexed downward and the preload on the bearings
will be increased. Paul Sayegh came up with the idea that if you
installed a washer of the correct thickness in between the ring nuts
that we could torque the top triple clamp nut, have the triple clamp
just touch the top ring nut enough to lock everything together, and not
transfer any additional load to the bearings. It is a good idea in
practice if you have a washer of proper thickness. I have never
seen a need for this but it does work. If the washer is too thick
then you can not torque the top nut to spec or if it too thin then it
negates the purpose. Some will say that you can lessen the torque
if your washer is a little too thick. You could but how much less
is still OK over the long haul?
If you have the experience to make this decision then do so.
Jamming the nuts on top of one another. This is the procedure that
I have personally used for years. All you
need to do is install the top nut finger tight, hold the bottom nut so
it will not turn, and turn it to the first position that aligns the
notches for the lock. Install the rubber washer and lock.
This is a no brainier, it locks the ring nuts and maintains proper
clearance for the top triple to be torqued to specs without effecting
the steering bearings. This method has been used and recommended
by the factories and eliminates guess work or mistakes. Or you
could use the factory set up that the bike came with and it too will
work just fine. Lets continue on with the assembly of the front
end. I'm going to use the jamming of the two nuts method.
The procedure is basically the same for all the methods. Screw on the
second ring nut finger tight and remember the rounded edge goes
down. Hold the lower nut, I just use pliers, and turn
the second nut so it aligns up with the notches. That is
all. Now check the bearing preload with the spring scale.
Remember we had 6 lbs and it should still be 6 lbs. If not then
you have let the first nut turn, the rounded edge is not down, or in
some cases the amount of turn on the second nut is
enough to flex the bottom nut. Sometimes you have to play a little
with the nut settings or positions. The idea is to get the 6 lbs
of pull. Remember here that the 6 lbs is an arbitrary number that
we just picked for demonstration purposes. The pull number of the
scales that was first recorded is the number we are always looking
for. Next install the rubber washer and lock and upper triple
clamp. Before installing the upper clamp wipe off any grease on
the shaft's taper section and the hole in the clamp. This is
suppose to be a dry fit. Torque the top nut to 80 ft lbs and check
the pull again. You should not see any change. Continue to
assemble the front end and keep checking the pull force. Torque
all bolts to spec three times. Now when you are done you have a
reference pull for your bike. Anytime you want to check the
bearings jack up the front end and do a pull test. If it different
then you need to find out why. I personally checked mine at each
oil change and after I set them up using this procedure they never
changed in 3 years of riding and my bike ran true to the red line in
high gear. When I did start to get some instability it was always
traced to tire profile or pressure. I also pulled the swing arm
and wheels twice a year to inspect the bearings clean and grease
them. This all may sound to be a little on the fanatical side to
some of you, but I was always riding up at speed ,and a stable
bike is very important to me . Remember that we are riding a high
performance bike with old engineering in it and it does require
maintenance to keep it safe at speed.
A few other things to mention here are 1 The Furbur Fix .... John
Furbur has the feel from doing this procedure 100s of times.
He can do it and it only corrects the problem of loose
bearings. I do not ever recommend people trying this
themselves. Every time that I have helped someone with their
steering bearings, and they have done the fix, I have found that their
bearings a too tight . You may get rid of the wobble, but usually the
result is instability in buffeting winds like what comes off a large
vehicle on the interstate. Leave the fix to John. If you see
him at a meet he will do it for free if he has the time. Lowering the
front forks .. the idea is to try to transfer weight to the front end .
This in theory works but it also derakes the front end which reduces the
front trail or castor effect. This can have a negative effect on the low
speed wobble. 17 inch wheels and radial tires ....... Remember that the
high speed wobble is a rear castor problem and is speed related. Just
the opposite of the low speed wobble the faster we go the less the
effect on stabilization there is. Smaller wheels and tires or less
rotating mass lessen the dampening effect on the high speed wobble. So
proper maintenance of all the bike's bearings become even more critical
when we mount radials on the bike . The radial tire does dampen better
than a biased tire but it is a quiet killer if proper maintenance is not
performed . The radial tire instills false confidence in a bike that is
not taken care of.