Ok I have a 2000 Honda 400Ex. I bought it from a guy here in Phoenix,AZ. I rode it around a bit and it was running ok. I go to start it up last week and ride around in the dirt for no more than a half mile and the bike just starts to bog and die. I go home and start tearing into it since now it only turns but doesn't start. It will give me a lil turn over but it quickly dies and doens't idle. So far I've found and changed a fouled spark plug, Confirmed i have nice blue spark when I hit the starter. I took apart the carb two days ago and found no gunk, however I did notice that the main jet was REALLY loose and seemed to just fall out when i started to disasemble. I downloaded a manual and checked valves clearances (they were tight before hand) and made sure they are up to spec. I'm new to quads and I hope I'm not missing something. Any ideas on where to go next? Even the smallest detail will be helpful, I'll also include pics if anyone wants to see something that I'm doing.