Just recently became owner of 18 hp ranch king. is it worth trying to fix?

It depends on how much financial input it needs to get it running and what your intended purpose is for it. If you just want an all-purpose around-the-acreage garden tractor, maybe some lawn mowing, and it only needs about $150US to get it going, then probably yes. If, on the other hand, the engine and transmission are completely shot and not rebuildable, then no. MTD Ranch King is not a particularly desirable class of machine for the average collector, but can still be a usable machine.