The piston/cylinder assembly for the O.S. Max .46 FX will not fit into the O.S. Max .46 SF engine. Because the .46 SF has been out of production for so long, parts for it are no longer available from us or O.S., in Japan. The engine was discontinued in 1994, when the .46 FX came out.

We'd not know where you may be able to locate the parts you need. You'll need to check online for parts, or place a "parts wanted" ad in places like the RCU Marketplace. Someone may be able to help you find the parts you need.