This engine has a 1-1/8" x 3.94" crankshaft on it. The replacement for the BS18 spec is the DS01S series. If you use the FH680V-AS41 or FH680V-BS36 engines, there may be minor differences like wiring, air breather, throttle and choke controls. Parts should be interchangeable as needed. The shaft is longer but can be cut down as needed.
