Hello Shane,
$850 sounds like you are purchasing it from "Ned Kelly Spares", most I have seen for is about $400. Try Ebay should be able to get one lot cheeper than that.
Before it gets to expensive, check that the brushes in the starter motor are ok, I had an incident where the starter was sluggish and found it to be only worn brushes, quick clean up of the commie with some crocus paper, new brushes, from memory not expensive, and back to normal operation.
I another thing I have experienced, is that some starter have washers between the stater mounting and the engine case, if they are required, and mising, it results in the starter cog messing with the flywheel to hard and makes the start sluggish.
Cheers Keith.
