ATK Motorcycles 604 1990 User manual

TABLE OF CONTENTS
Starting Procedure Page
Cold Start .......................................................................... 2
Warm Start ........................................................................2
Downhill Start ....................................................................2
Front Fork
Operational Maiiltenance ...................................................3
Oil Replacement .................................................................3
Preload Adjustinent ............................................................ 5
Spring Rate ........................................................................6
Rear Shock
Rear Suspension Sag ......................................................... 7
Compression Dampening ...................................................8
Rebound Dampentng..........................................................9
Chain Adjustment
Chain Tension .................................................................. 10
Chain Maintenance .......................................................... 10
Brakes
Brake Fluid ...................................................................... 11
Brake Pads ...................................................................... 11
Bleeding The Brake .......................................................... 11
Carburetor
Idle Adjuster .................................................................... 13
Air Filter Cleaning ............................................................ 13
Engine Maintenance
Oil I..evel ........................................................................... 14
Oil Change ....................................................................... 15
Oil Filter Replacement ...................................................... 16
Oil Sump Screen Cleantng ................................................ 16
Clutch Adjustment ........................................................... 17
Cam Belt Adjustment ....................................................... 18
Valve Adjustment ............................................................. 19
Igllitlon ............................................................................ 19
Technical Data .....................................................................20
Table of Contents

STARTING PROCEDURE
Cold Start
Step One: Tum the fuel petcock to the open position.
Step 1\vo: Pull
the choke up to the open position.
Step Three: Prime
the engine. Kick the engine over until the
compression ls high. Pull the compression release
in a little - just to get over the compression. Repeat
this a few tunes.
Step Four: Line
up the white mark on the Urning window and
give it a hard kick with the throttle slightly open.
From
our experience. 99% of the time the engine
will start on the first kick.
Electric Starter
Skip steps Three and Four and press the starter button.
Warm Start
To start the engine when it is warm. just line up the white mark
on the Urning window. and kick it with the throttle slightly open.
Down Hill Start
Shift the engine into neutral. then push the compression
release on
and coast the bike up to speed. Once up to speed. shift
the engine into second gear without the clutch. Let the engine
tum
over a few times. then release the compression lever. The engine
should
start right up.
2 Starting Procedure

FRONT FORK
Operational Maintenance
To achieve optimum performance from your White Power 4054
front forks. follow these maintenance procedures.
After every two races
or eight hours of riding, loosen the
breather plugs (located on top of the upper fork cap) a few turns to
release
air pressure build-up. Also. pull the fork wipers down and
clean around the seal area after a build-up of dirt occurs. After
every four races
or thirty-five (35) hours of riding. or when damping
becomes erratic, change
the fork oil.
Oil Replacement
To replace the fork oil. loosen the breather plugs to release any
air pressure built up in the fork. Loosen both the upper fork cap
and lower fork cap approximately one tum. Remove the front wheel,
brake caliper
and the brake line guides. Do not remove the brake
line from the caliper. Remove the fork tube from the triple clamps
and tum the fork upside down. The bottom fork cap should be
facing up. Unscrew the bottom fork cap and remove the preload
spacer and fork spring. Drain the fork oil and pump the fork a few
times to drain the remaining oil. Replace the fork spring and
preload spacer. and screw on the fork cap. Tum the fork over and
unscrew the top cap and compress fork slightly to remove the half-
moon washers. Pull
out the keeper by pressing on one side and
compressing the fork. Remove the bottom-out buffer and nylon
spacer.
Tum the fork over and drain the remaining oil.
Next. compress the fork
so you can see the bypass valve. Take a
thin rod (1/8" or less O.D.) and lightly depress in one of the six
holes
in the valve as shown in Figure l (Page 4). This will allow the
oil to drain down to the lower fork leg when poured. The standard
oil level measurement location in the White Power 4054 fork iS
where the oil comes up flush with the dtstance between the top of
the dampening rod to the top of the outer fork top, as shown in
Figure 1.
Front Fork 3

From our racing experience, we recormnend the oil level be
flush with the top of the bleed valve when the dampening rod is
extended 4-1
/2" (130mm) from the fork tube. We recommend
Bel-Ray
HVI lOW shock and fork oil.
Figure 1
H.Al.F·MOON-......_ 1-
WASllFAS I 0
Bl/FFE/l C::7
'
QllMPENBVG RO()
EXTENSION lENGTH
t
FORI<
T(/fiE
8L££'0 VALYE
The quantity of oil in the fork- 20 to 23 ounces of 10 weight oil
only affects
the last fifty per cent of the travel. The more oil in the
fork, the less the fork will have a tendency to bottom out. Never
exceed
an oil level height of 5-11/ 16" (150mm) and never go below
3-15/ 16" (120mm).
EXAMPLE:
(STANDARD)
4 Front Fork
Dampening Rod Length
From Oil
Level
3-15/ 16
11
5-1/8"
5-11/ 16"
(120 mm)
(140mm)
(150 mm)
Fork Action
Soft
Medium
Hard

The standard free length of the rear spring is approximately
8-11I16" (220 cm). This length can vary slightly from spring to
spring. The preload
should be approximately 1I4" (6 mm). (If the
preload falls out of the 1/8" -1/2" dimensional boundary whlle
obtaining the
2" -3" of suspension sag, a heavier or lighter spring
rate is necessary.)
EXAMPLE:
Sag
2" (50 mm)
3" (76 mm)
3
11
(76 mm)
2" (50 mm)
Preload
7I16" (11 mm)
1/4" (6 mm)
5/8" (16 mm)
1/8" (3 mm)
Spring Rates available:
Kg/mm 8.7 9.2 9.7
Lb./in. 485 515 540
Preload Adjustment
Comments
Good
Good
Heavier spring
rate needed
Lighter spring
rate needed
To
change the initial stage of travel in the fork. decrease or
extend the length of the preload spacer. By decreasing the length of
the preload. the inltial travel will be softer. See Figure 2 for preload
measurement.
Figure 2
SPACER
@) @
Front Fork 5

EXAMPLE:
Spring Rate
PRELOAD LENGTH
O" (Omm)
3/16" (5 mm)
3/8" (10 mm)
FORK ACTION
Soft
Medium
Hard
If the fork action ts too stilT through the entire range of travel
while using the shortest dampening rod length
and the shortest
preload length, we recommend changing the standard 25 lb. fork
spring rate to a 23 lb. fork spring rate. The spring
rate can be
changed by adding a small primary spring to the
main spring. See
Figure 11tree for installation.
Figure 3
c3 LB.
cl LB.
S,tff>/NG !<AT£
SPRING !?ATE
(STANOARLJ)
--- ---- -- __ __..,. __
6 Front Fork -Preload Adjustment
SHORTEI? r'/?ELOAtJ
SPACER
• 9 2 P/i/A'IAAY
S.Pl?ING

REAR SHOCK
Rear Suspension Sag
The rear suspension should sag 2" - 3
11
(51 - 76 mm) when
sitting on the bike in normal Iiding posltlon. This small sag
requirement ls due to the A-Track Chain Torque Eliminator. which
increases
the usable rear suspension. From our expeiience. we
recommend
that for motocross racing, 2" to 2-1 /2" (51 - 64 mm) of
sag ls best; for trail Iidlng use up to 3" (76 mm).
Prop
the bike up on a center stand so the rear wheel ts off the
ground, thus unloading the rear spring of the bike's weight.
Measure
the distance between the center of the axle to the center of
the left side number plate's rear attachment screw (as shown in
Figure 4). This distance ls the extended travel length.
Take
the bike off the stand and sit on it in your normal riding
position. Measure the new distance between the center of the axle
to
the center of the left side number plate's rear attachment screw.
The distance ls the usable travel length.
Subtract the usable travel
length from
the extended travel length. The difference between the
two equals the suspension sag.
(Extended Travel Length -Usable Travel Length) =
Suspension Sag
Figure 4
lENGTH
t
Rear Shock 7

To achieve your desired suspension sag it will be necessary to
adjust
the rear shock's preload. The preload is equal to the free
length of
the rear spring minus the compressed length of the
spring.
(Free Length -Compressed Length) =Preload
Figure 5
CaHPl?ESSIOV.
AlJJUSTER
N'80UND
A[)Jl/STfR
P//ELOAIJ
AfJv/JSTEA
Compression Dampening
The compression dampening adjustment knob is shown in
Figure 5. There are seven (7) compression settings from which to
choose.
Tum the knob counterclockwise until it stops: at this
position the compression dampening is
set at the softest rate. To
increase dampening. tum the adjustment knob clockwise one
setting
(click} at a time.
There is no
standard setting for the compression dampening:
this ls determined by
track conditions and each rider's ability .
From
our racing experience, we recommend you set the
compression dampening between one (1)
and four (4).
8 Rear Shock -Rear Suspension Sag

Rebound Dampening
The rebound dampening adjustment wheel is located under the
spring retainer as shown in Figure 5. There are eleven (11) rebound
settings from which to select. Setting one (
1) is the weakest
absorption -
the shock absorber extends fast after compression.
Setting eleven (
11) is the strongest absorption - the shock extends
slowly after compression. Like the compression dampening,
the
rebound dampening does not have a standard setting. From our
racing experience. we recommend you set the rebound dampening
between four
(4) and seven (7).
Rear Shock 9