I hear a good number of people say that they will change oil and do a good maintenance round before a tough ride. "Tough" varies, of course, but here I am talking about a long day ride, paved and dirt, for a total of about 400 miles. So, my question: The oil on my 640A is at full, but has 2000 miles on it. I use the Motorex synthetic stuff. Do I want to change it before the 400 mile day ride next Saturday? To rephrase: It is a busy week and I'd rather ride than work on the bike on Saturday Thoughts? Experiences?