I recently got a 2011 Yz450f. It had an oversized tank on it when I bought it. It started 1st kick. Then I took oversized tank off and put stock on it. It then started 3rd kick. It idled and then I went to take off and it killed. Now it wont start. I hear it hit. I push started it and it just wont start. I tied a rope too it and was pulled. It started but died immediately after. The bike has a lot of compression. I checked the plug and it was fine. I'm not sure what happened? Is it fuel pump or something? Help please!