please help me ! when i got the bike the oil red bulb turns on with the switch on and when start the engine then goes off. that was in the first times. now never turn on i change the bulb but nothig .. can I get some help here !

Pull out the light, and buy another one just like it.  It really is that easy.

i change the bulb and still without turn on ! if that is what you mean ..

Ok, yes re-reading your post I realize that you said you changed the bulb already.  It took 2-3 times, though. 

You can check the sensor directly using a voltmeter or hooking a 12V light bulb directly to it and the + terminal of the battery (I think).  If the sensor's busted, you probably have to replace it.  I don't know if stuff like that is fixable.

Or you can check your oil level regularly (like you're supposed to) and never worry about the light.  It's not called a "too late light" for nothing.

yeah ! you are correct. its not a big deal ! but i like the bike in full functionally thats the way 1 start to abandon things first dont worry about that!! then dont worry about that too and that and that !!!! next year i will have a delivery bike !