The vehicle is a KTM Duke 200. Before I washed the motorcycle it was working fine. After washing the engine is overheating. More than 6 points in meter. The radiator fan is not turning on. Please give me solution.
I'm not overly familiar familiar with the Duke so this advice is a bit generic but here we go -
First check if the fan itself has failed (if your bike is the RC390 I believe they are a known weakness), you should be able to disconnect the fan and wire power to it directly, if it runs then you know the fan itself is okay and the problem is with the bike controlling the fan and that's probably an electrical issue somewhere.
Check all the connections for the fan and for any coolant temperature sensors (assuming the bike has them!) - make sure nothing has worked loose during the washing as this could cause it, while you are doing this it's also worth taking the connections apart and making sure the contacts are clean and dry before reconnecting them. Assuming all that is done/okay if the fan still isn't operational check the fuse(s) for the fan (again assuming the bike has them) are clean, correctly seated and not burnt out.
You could also be looking at a coolant system issue - check all the hoses and make sure there aren't any leaks and with the bike up to temperature check for any hoses that are stone cold as this may indicate an airlock or similar. Beyond that you could be getting into things like the thermostat and you are probably best off taking it to a mechanic/dealer.