guarantee you its just the tuning if you can get it to hit for a second or two, and you know for sure that there are no problems with fuel feeding.

tuning...

high speed screw should be 4 turns counter clock from stopped
low speed should be flush with the edge of the slide valve. about 1.5 turns from stopped

this might help with the fine tuning

http://www.traxxas.com/support/kb_se...&highlight=276