unity landscape issue

hello guys, i am working on a racing game for iPhone whose default orientation is landscape. i have set the orientation in PlayerSetting → Resolution and Presentation to landscape right. but when i run the app on iPhone and use the accelerometer to turn the bike it gives me effect like its orientation is being changed. but after having that effect orientation remains same.

can anybody guide me why this effect i am getting?
any help will be appreciative. thanks

Add this to your code:

#if UNITY_IPHONE
	iPhoneKeyboard.autorotateToPortrait = false; 
	iPhoneKeyboard.autorotateToPortraitUpsideDown = false; 
	iPhoneKeyboard.autorotateToLandscapeRight = false; 
	iPhoneKeyboard.autorotateToLandscapeLeft = false;
#endif