"83 EZGO Fuel delivery issue

[Motorman 007]

I have an '83 Marathon with the 244cc Robin engine. It had a cracked case when the starter/generator mounted to the case. I was able to locate a used engine that had a bad jug and piston and this past weekend, I swapped my "good" jug and piston over to the other engine. I now have no fuel at the carb. It appears that the fuel pump works on crankcase vacuum/pressure?? I've got good compression and spark but it won't run. I swapped both the carb and the fuel pump to be sure since I know it ran before the jug and piston swap. Any suggestions as to what I should look for? Is a low pressure electric pump a viable solution? Thanks in advance.