Canuck:
I have to assume since you did not specify the engine is mounted on the airplane? If so and before, it ran fine here is what I would look for,

1. If installed on the plane. Make sure the clunk is still attached to the pickup tube. They have a tendacy to fall off. Use a zip tie to secure the tube to the clunk.

2. If not installed on the airplane and you can visibly see the fuel line ensure it is not floating on top of the tank and re-read #1.

3. If your plumbing is good to go, you will more than likely have to take the carb apart and perform a cleaning of the screens. If memory serves there will be 5 screens. 3 you can see and two you cannot. If the engine has sat up for awhile it is possible that there may be some oil mix clogging the screens. I will tell you in advance that you can buy a rebuild kit for the Walboro carb at your local lawn mower repair shop, however if you are careful you will not need one unless the diaphragm is cracked.

When you disassemble the carb make sure you put the reed valves back on the same way they came off. It is very easy to get them 180 degrees out and they only like to work in one direction.

Use brake cleaner and spray the orifices if possible spray them in the reverse of the way the fuel enters the carb. Do a thourough visual inspection and re-assemble. Pay particular attention to rips or tears in the reeds and the diaphragm,

Hope this helps you somewhat.

Good luck.

Glenn