The FXi is the RTF trainer version of the FX. It has a low compression head. Therefore is easy to start and adjust but doesn't have as much power as the original FX. The FXi also has needle valve setting restrictors.

The FXi has a lot more power than the LA series engine.

The FXi is easy to spot among FX engines as the head fins are rounded front and rear like on a LA engine. It also has the needle valve restrictors.