Hey guys I need help with my quad. I went to buy a 2000 DS650 from a guy that needed a clutch. He fired it right up with no problems and let it run for a couple minutes. It sounded great. We loaded it up in my truck and drove home. After we got it out of the truck, we tried to start it up and nothing. We kept trying and flooded it. Took the spark plugs out, dried them off and let it sit for a while. Tried to start it again and nothing. I got new spark plugs and have great spark and still no start. I checked the timing and everything lines up at tdc. Tried a new cdi box and still nothing. It will turn over great but no start. It has compression, spark, and fuel. I don't know what else to look for. Maybe valve adjustment? I just don't understand how the guy could start it right up and then nothing when I get home. Any ideas would be greatly appreciated.

Thanks!!