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MAINTENANCE WORK ON CHASSIS AND ENGINE »
ENGLISH
43
when engine is cold
10 mm
3
4
5
6
1
1
2
400/450/525 250-F
Cooling system
Coolant is circulated by a water pump [1] located in the engine. When the
engine is cold the coolant only circulates through the cylinder and the cylin-
der head. After the engine has reached its operating temperature (about 70°C,
158°F), the thermostat [2] opens and the coolant is also pumped through
both aluminum radiators.
Air blowing in through the radiators cools the coolant. The slower the speed
of the motorcycle, the less the coolant is cooled down. Dirty
radiators also reduce the cooling efficiency.
Pressure induced by heating of the coolant in the system is controlled by a
valve in the radiator cap [3]; a water temperature rising up to 120° C
(248° F) is admissible, without fear of problems.
– If possible, always check level of cooling liquid when the engine is cold.
If you have to open the radiator cap [3] when the engine is hot, use a rag
to cover the cap and open slowly to release pressure. Caution - scalding
hazard!
– Do not detach any radiator hoses while the engine is hot. The escaping
hot coolant and the steam may cause serious burns.
– In case you get burnt, hold the affected part of your body under running
cold water right away.
– Coolant is toxic. Keep the coolant out of the reach of children.
– In case coolant is ingested, consult a doctor immediately.
– If coolant gets into your eyes, rinse them out with water immediately and
consult doctor.
A mixture of 50% antifreeze liquid and 50% destilled water is used as coolant.
However, the antifreeze protection must be at least -25° C (-13° F). This mix-
ture offers antifreeze protection but also good corrosion protection and should
therefore not be replaced by pure water.
– The cooling system must be bled after draining the cooling liquid or after
adding more than 0.25 l (0.06 US gallons) cooling liquid.(see below).
– For the cooling system, use only high-grade antifreeze (e.g. Motorex Anti
Freeze). Using lower-grade antifreeze agents can cause corrosion and
coolant foaming.
– Extreme climate conditions or stop and go traffic may cause overheating
problems. To avoid this, an electric blower [4] is offered (ask your KTM
Dealer).
Checking the coolant level
The coolant should be 10 mm (0.4 in) above the radiator fins when the engine
is cold (see diagram). In the event of the coolant being drained, always fill
and bleed the system.
If possible, always check the level of cooling liquid when the engine is cold.
If you have to open the radiator cap [3] when the engine is hot, use a rag to
cover the cap and open slowly to release pressure.
Caution - scalding hazard!
Bleeding the cooling system (400/450/525)
By removing the screw [5] at the front end of the cylinder you can drain the
coolant.
To bleed the cooling system, fill in approx. 0.8 liters (0.2 US gallons) of coolant
and remove the bleeder screw [6]. Do not reinstall the bleeder screw until
coolant escapes at the bore without any bubbles.
Then, fill in the coolant until it reaches a level about 10 mm above the
radiator fins.
After a short ride, check the coolant level once more.