There was a little bit in the tank when I took the bike home, so my dad and I pulled the hose on the bottom of it that supplies the fuel from the tank to.... well, wherever it goes. I drained the petrol that was in it, into a container, and my dad put some fresh petrol in. We shook the tank around a bit and drained out the clean stuff we'd just put in. Then we hooked the hose back up and put fresh petrol in. So the petrol should be clean.
Nothing got done today coz dad was busy ... doing nothing, but still, he didn't want to help me. Grrrr!