I changed my oil today for the first time and when I pulled the filter out it was clogged with a lot of black crud!! Is this normal? I have only put on about 250kms on it. I have been in some major mud and water though. I thought I have read here before something about the first filter change and there being a lot of crap in the filters, but not to be alarmed, is this true, or should I be concerned? I am starting to think that I am not meant to own a 4 stroke and think I might have to go back to a 2 smoker next year!!