I have a FZ63 that's about 2yrs old but with only about 1 1/2 gallons of fuel run through it. I have this engine in a u-can-do, using PowerMaster 20/20, OS F plug, APC 14x4w prop. This engine was running great a couple of weeks ago then I wanted to change my CG so I had to pull the engine out, reinstalled it in the plane & I can't get it to run now. At first I thought I might have crossed the fuel & pressure lines but I checked & it's connected as it should be. Cleaned /inspected the regulator & still will not run. A couple of times I did get it to run for about 30 seconds by adjusting the HSN to about 3 turns open but this was only a rough idle & wouldn't take any throttle at all. When I turn the prop by hand to prime it I can hear a hissing coming from the carb(never heard this before) & it's leaking fuel from the carb.
Any thoughts on what this problem might be ?