I had my engine start 3 times today, I brought the bike into my garage to tighten the chain back up and went to make a sandwich. When I came out to start it again to go get my check, the engine would turn over and start and I was getting fuel in because it revved ip and down the way it should, but as I was pedaling the bike started to slow down and eventually stop, never getting to actually ride without pedaling and somehow never got the engine to run on its own. What could this problem be? Everything is brand new, plug is fine, gets spark under conpression and without. Its just when I pop the clutch, give it gas and keep pedaling that it starts to slow itself down and turn itself off