Yup, Hogflyer is correct. I have one of these engines, and although I like it, it is a bit temperamental. It will not draw fuel through a filter, so tank placement is going to be very important as well. You must have the center of the tank on the same level as the carb fuel inlet.

Also, mine had a loose and poorly sealed crankcase backplate that caused all kinds of grief. I fixed it by removing the backplate (it screws into the crankcase) and sealing it with a couple of wraps of teflon plumbers tape and then screwing it back in really tightly.

The fuel line can be flexible, just make sure it hasn't kinked against anything.

Good luck,

Phil