My OS 40LA didn't start after a winter in storage. I hadn't been taking care of it while in storage so a friend suggested I disassemble it completely, remove any rubber parts and soak/clean it in methylated spirits. However one of the carburetor screws was so tightly fit that I didn't have a chance getting it out. It ended up ruined. Without the proper equipment to drill it out I decided to reassemble the engine. However I can't get it satisfactory. The piston and the sleeve around it seems to fit badly. I can get them both in, but the piston won't turn smoothly. In fact, it won't turn more than in the bottom half. Any idea why the piston doesn't fit properly? Is it supposed to be aligned in a special direction?

As for the engine not starting; it did run for about 2-3 seconds, but it seems to not be able to draw fuel. Turning the prop manually didn't draw fuel into the carburetor, only if I blew into the pressure hose (normally connected to the silencer.) I might be wrong, but is there anything that may cause the engine not to draw fuel?

Without seeing the engine, we'd not know if there's a problem in the assembly.

The engine should be tight when the piston moves to the top of the stroke. See the O.S. Max FAQs about this. It's normal for ABC-type engines.

Usually, a Craftsman #2 screwdriver will fit into the carburetor retaining screws and allow you to remove them. Most American Phillips-type screwdrivers are too pointy, and need to have the tip ground down a bit so that the screwdriver properly fits into the screws.

If the liner's not installed properly, the engine won't draw fuel or run, since the ports won't be lined up correctly.