My motorbike has been suffering from an issue which goes like this . Whenever I drive for a few kilometres a smell comes from the engine oil sump area even if the engine oil is brand new . One year ago when I replaced this engine oil with another then that particular issue dissappeared . Now it makes me confused whether this problem was due to engine oil or other else
Is the coolant circulating OK, and does the coolant temperature behave as it should? How about the oil - can you check that it's actually circulating round the engine? How's the oil pump? (I'm just throwing guesses out by the way - I'm not sure if motorbike engines even have similar cooling systems to what you'd find in a car).