KTM 50 SX JUNIOR - Manual (Page 19)

ENGLISH
18
MAINTENANCE WORK ON CHASSIS AND ENGINE
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Basic suspension setup for the weight of the driver
To achieve maximum handling performance and to prevent the telescopic fork
and shock absorber from being damaged, the basic setup of the suspension
components must be suitable for your child's weight. At delivery, KTM's mini
motorcycles are set to accommodate a driver weighing 25 - 30 kg (wearing
full protective clothing). If your child's weight exceeds or falls short of this
range, you will need to adjust the spring preload for the telescopic fork and
shock absorber accordingly.
To adjust, check the sag of the shock absorber and telescopic fork. The motor-
cycle should be filled up and your child should be wearing full protective
clothing.
To determine the sag of the shock absorber
– Jack up the motorcycle until the rear wheel no longer touches the ground.
– Measure the vertical distance between the rear wheel axle and a fixed point
(e.g. a mark on the side cover) and write it down as dimension A.
– Place the motorcycle on the ground again.
– Have your child sit on the motorcycle in a normal seating position
(feet on the footrests) wearing full protective clothing and bounce up and
down a few times to allow the rear wheel suspension to become level.
– Holding your child and the bike, have another person measure the
distance between the same two points with the load on the motorcycle to
establish dimension B.
– The sag is the difference between dimensions A and B.
EXAMPLE:
Motorcycle jacked up (dimension A) . . . . . . . . . . . . . . . . . . . . . .400 mm
Motorcycle on ground with driver seated (dimension B) . . . . . . .– 355 mm
Sag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45 mm
50 SX Junior shock absorber sag . . . . . . . . . . . . . . . . . 45 mm (± 5 mm)
50 SX shock absorber sag . . . . . . . . . . . . . . . . . . . . . . 50 mm (± 5 mm)
If the sag is lower, the spring preload of the shock absorber must be reduced,
if the sag is higher, the spring preload must be increased (see Changing spring
preloading of the shock absorber). A harder spring is also available for the
50 SX (see spare parts catalog).
To determine the sag of the telescopic fork
– Jack up the motorcycle until the rear wheel no longer touches the ground.
– Measure the distance between the upper edge of the slider tube and the
triple clamp and write it down as dimension C.
– Have your child sit on the motorcycle in a normal seating position
(feet on the footrests) wearing full protective clothing, and bounce up and
down a few times to allow the telescopic fork to become level.
– Holding your child and the bike, have another person measure the
distance between the same two points with the load on the motorcycle to
establish dimension D.
– The sag is the difference between dimensions C and D.
EXAMPLE:
Motorcycle jacked up (dimension C) . . . . . . . . . . . . . . . . . . . . . .200 mm
Motorcycle on ground with driver seated (dimension D) . . . . . . .– 160 mm
Sag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 mm
50 SX Junior telescopic fork sag . . . . . . . . . . . . . . . . . 30 mm (± 5 mm)
50 SX telescopic fork sag . . . . . . . . . . . . . . . . . . . . . . 45 mm (± 5 mm)
If the sag is lower, the spring preload of the telescopic fork must be reduced,
if the sag is higher, the spring preload must be increased.
The preload on the fork spring is determined by the length of preload spacer
[1]. If an adjustment is necessary, demount the fork legs, remove the plugs
and shorten the pretensioning sleeves or replace with longer ones
(see maintenance of telescopic fork). Harder fork springs are also available
for both models (see spare parts catalog).
A
B
C
D
1
A
B
C
D