Three possibilities:
The carburetor is set to run too rich, the plug is fouled and is not get sufficient spark, or there is a leak.
Start with the leak and work backward: leak, spark, carb.
what is the gas/oil mix for the 24cc weed trimmer by craftsman
40:1 owner's manual for a homelite st 185 trimmer says 32:1
50:1 gas to 2 cycle oil.
40 to 1
50 to 1
40:1
50:1
25:1
32:1 (4 oz. oil to 1 gallon of gas)
32 to 1 32 to 1
To replace the gas tank on a Sears weed trimmer, first ensure the trimmer is turned off and unplugged. Remove the screws or bolts holding the existing gas tank in place, usually located near the engine. Carefully disconnect the fuel lines, taking note of their placement for reassembly. Install the new gas tank by reversing the process, securing it with screws, and reattaching the fuel lines.
You can get them at Home Depot, Lowes, and some small repair shops.