LO206 won't start when on the ground.

So I've finished my kart after 2 months of work and I did the break-in runs on the stand just fine but when its on the ground it wont start at all. I've had it turn over a little bit, maybe for one second, but it died right after. I just ran it again on the stand fine so nothing broke in between the tests and the ground. Any idea what I can do to remedy this?