If you have the starter with the black battery case hanging off the bottom, bear in mind that the battery supplies insufficient current/voltage to the starter for larger engines.

I have one of these.

I rigged it up so I could unplug the spade connectors, and use a second cord with male spade connectors hooked to the field box, to start the bigger planes.

That way I can always go right back to using the battery pack on smaller engined planes whenever I want.