Hi brand new member. I realise that this thread is over a year old, but I have just bought a series one and the oil cap has threaded. I'm not sure anyone has ever put oil in it as its only done 1800 miles since new. Its in immaculate condition other than the threaded oil cap. my question is simple, I can't get the cap back on properly so its not sealed. Does it need to be for me to ride. I mean I know that I have to make sure that stuff doesn't get in, but can I ride with it loose. I ask because it has an o ring which suggests that it has to seal, but is that just to stop water?