4 oil changes in 1900 miles???? really?? Please dont tell that to the dealer, it will be obvious you have no clue what you are doing... under UK/EU law, dealers cannot force you to have the bike serviced by the main dealer in order to keep the warranty, but if they can prove the failure is due to the bike not being serviced correctly then they will win. So, you need to read the service schedule properly, if asked you explain thats what has been done to the bike and leave the bike with the dealer to fix and hope the other mechanic didn't leave too many telltale signs that he's been in there, and that he used genuine parts! why you decided to take it to another mechanic I have no idea... but so long as the other mechanic is a proper business, you may still be ok.