KTM 125 SX - Manual (Page 18)

ENGLISH
17
MAINTENANCE WORK ON CHASSIS AND ENGINE
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Checking the basic setup of the telescopic fork
The precise riding sag of the telescopic fork cannot be determined for vari-
ous reasons. Similar to the shock absorber, smaller deviations in your weight
can be compensated by adjusting the spring preload. However, if your tele-
scopic fork bumps frequently (hard end stop during compression), you should
install harder fork springs to avoid damaging the telescopic fork and frame.
Changing the spring preload on the telescopic fork
The telescopic forks for these models must be partly disassembled to adjust
the spring preload (see WP manual). Pretension spacers are available in
heights of 1.5, 2.5, 5 and 10 mm (see spare parts catalog). The fork springs
may not be pretensioned by more than 20 mm.
NOTE:
WP precisely adjusts the spring pressure by inserting pretension spacers.
Fluctuations in production are compensated with pretension spacers in vari-
ous heights. This can cause the fork springs in the fork legs to have different
degrees of pretension. Fork springs and pretension spacers should always stay
together.
Replacing fork springs
If you weigh less than 75 kg or more than 85 kg, you should install the respec-
tive fork springs. The correct spring rate is shown in the illustrations. The stan-
dard spring is shown in bold print. The type number of the telescopic fork is
embossed on the inside of the fork leg axle passage.
If you are uncertain which spring to use, contact your KTM workshop.
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
spring.
Breather plug front fork
After every 5 hours of use for competitive racing, slacken the breather
plugs [1] a few turns in order to relieve excess pressure from the inside of the
fork. To do this, place the motorcycle on a stand with the front wheel lifted
off the ground. When riding the motorcycle mainly on the road, it will suffice
to have this job performed in the course of the periodical maintenance
service.
Excessive pressure in the interior of the fork can cause leaks in the fork. If
your fork is leaking, it is recommended to open the breather plugs before hav-
ing the seals replaced.
1
65
Spring rate
70 75 80 85 90 95
Riders weight inclusive gears in kilogram
4,6 N/mm
4,2 N/mm
for example 250 SX
4,4 N/mm
MODELL SOFTER STANDARD HARDER
12187C01 (125 SX) 432.455.00.040W 432.455.00.042W 432.455.00.046W
12187C03 (250 SX) 432.455.00.042W 432.455.00.044W 432.455.00.046W
Cleaning the dust sleeves of the telescopic fork
The dust-protection bellows [2] are to remove dust and coarse dirt particles
from the fork tube. However, after some time, dirt may also get in behind the
dust-protection bellows. If this dirt is not removed, the oil sealing rings located
behind it may start to leak.
Use a screwdriver to lift the dust-protection bellows out of the outer tubes
and slide them downward.
Clean the dust-protection bellows, outer tubes, and fork tubes thoroughly, and
oil them thoroughly with Universal oil spray (Motorex Joker 440) or engine
oil. Then, push the dust-protection bellows into the outer tubes by hand.
No oil may reach the front tire or the brake disks since this would consider-
ably reduce the tire's road grip and the braking effect of the front brake.
2