I have a featherlite 20cc weedeater which has worked great for 4 years. Now the primer bulb stays compressed and it won't run for more than 10 seconds. I have dumped out gas and put in new, taken apart carb. And cleaned filter. Tried opening gas cap in case air valve in cap was blocked. Next I am putting in a new spark plug. Any other ideas?

Have you tried replacing the fuel line from the motor to the gas tank?

If you pushed the primer in and it doesn't come back on its own you need to replace that bulb before doing any other work, you may have a blocked line going to the tank.