Laylavmax1200

Hello everyone. First post here. Great forum. I built a 1974 DT175 for the wife. Lots of piston slap so I took Topend off and was bad. I've got an old 1971 CT175 I was going to restore with brand new top end. So I mounted it on the DT. Only custom I had to do was add 1/2" spacer to carb and cylinder. It ran before but not now. Sucks! I cleaned carb out so good you could eat off it. But I can't even get gas to the carb. Just small amount that's left in fuel filter. I've got spark. Don't know what to do. Can't redo the DT Topend right now. Too much $. Am I wasting my time trying to Frankenstein this? Also, what's with the different carb? I know '74 has reeds and '71 piston port but is that lever on the '71 the choke? It doesn't help. Please if someone can help, help me. Thank you. And thanks again for this great forum