Oil color will and should change. Its a sign that its doing its job properly.
Don't pay attention the 'color' of oil. Notice the performance. If you feel a drop, then make sure your bike is well tuned (change spark plug if more than 1 year old, clean air filter, get tappets and carbs adjusted, apply lubricants on chain etc etc)
You don't need to use any cleaning agent to clean your engine. If you still wish to clean it, just change the next oil 'early', say after 500kms.