KTM 250 SX-F 2007 Owner'S Manual Download Page 18

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ENGLISH

MAINTENANCE WORK ON CHASSIS AND ENGINE

Basic suspension setup for the weight of the driver

To achieve maximum handling performance and to prevent the fork, shock

absorber, swing arm and frame from being damaged, the basic setup of the

suspension components must be suitable for your weight. At delivery, KTM's

offroad motorcycles are set to accommodate a driver weighing 75 - 85 kg (wearing

full protective clothing). If your weight exceeds or falls short of this range,

you will need to adjust the basic setup for the suspension components

accordingly. Minor deviations in weight can be compensated by adjusting the

spring preload. Different springs must be installed for larger deviations.

Checking the shock absorber and spring

You can establish whether or not the shock absorber spring is suitable for your

weight by checking the riding sag. The static slag must be correctly adjusted

before the riding sag can be determined.

Determining the static sag of the shock absorber

The static sag should be as close as possible to 33 mm (250 SX-F) or 35 mm

(450 SX-F). Deviations of more than 2 mm can strongly influence the

motorcycle's performance.

Procedure:

– 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.

– Ask a helper to hold the motorcycle in vertical position.

– Measure the distance between the rear axle and the fixed point again to

establish dimension B.

– The static sag is the difference between dimensions A and B.

EXAMPLE:

Motorcycle jacked up (dimension A) . . . . . . . . . . . . . . . . . . . . .600 mm

Motorcycle on ground, unloaded (dimension B) . . . . . . . . . . . . .– 567 mm
Static sag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 mm

If the static sag is lower, the spring preload of the shock absorber must be

reduced, if the static sag is higher, the spring preload must be increased. See

chapter "Changing the spring preload of the shock absorber."

Determining the riding sag of the shock absorber

– Have a helper hold the motorcycle while you sit on the bike 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.

– Stay on the bike and have another person measure the distance between

the same two points and write it down as dimension C.

– The riding sag is the difference between dimensions A and C.

EXAMPLE:

Motorcycle jacked up (dimension A) . . . . . . . . . . . . . . . . . . . . .600 mm

Motorcycle on ground, loaded (dimension C) . . . . . . . . . . . . . .– 493 mm
Riding sag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .107 mm

The riding sag should lie between 102 and 112 mm.

If the riding sag is less than 102 mm, the spring is too hard (the spring rate

is too high). If the riding sag is more than 112 mm, the spring is too soft (the

spring rate is too low).

The spring rate is written on the outside of the spring (e.g. 63/250). The type

number of the shock absorber is embossed on the bottom of the tank.

The illustrations show which spring should be installed. The standard spring

is shown in bold print.

After installing a different spring, readjust the static sag to 33/35 mm (± 2 mm).

According to our experience, the damping rate of the compression stage can

remain unchanged. The damping rate of the rebound stage can be reduced

by a few clicks for a softer spring or increased by a few clicks for a harder