Murray riding mover was running OK. Took a short break and came back to start up and when I turn the key...nothing. Took the battery out and had it checked--its good. Replaced the fuse and tried again but when turning the key...nothing happens. Any ideas as to why to try next. I thought it might be the ingition switch but that looks pretty hard to replace. Anything else before I try that?

As fix_it stated, they can rust on the axle and, in my case ('87 Wards LT), be virtually impossible to get off (bent the puller, burned the paint while using a torch, copious amounts of Kroil, lots of BFH application, all to no avail. I needed to replace the rear tire. What I finally had to do (with someone's recommendation on this forum) was to physically tip up and roll the tractor onto its side, and cut/saw that ^^%%#@#(^ tire off! Even that wasn't easy because there is still the steel wire reinforcing around the bead of the tire that I had to get under to cut. Hope yours comes off easier.

The iron sleeve might be replaceable, but is it worth it? I wouldn't think so. It should hone up and last forever. Sometimes older motors aren't made anymore and you are referred to the newer engine, such as the 13.5 The mounting surface of most of the larger Briggs are exactly the same, so a wide range of HP will have the same crankshaft length and bolt mounting pattern. The differences might be where the throttle cable attaches or the location of the carb. Did you try Tulsa Engine warehouse for a short block? They are much cheaper and you can transfer your old stuff to the new shortblock. You might even find a used engine on ebay.

Seat switch is open when seat is occupied. Seat switch closes when seat is vacant. Closing the seat switch connects the magneto kill wire to ground, stopping the spark production and causing the engine to quit running. The clutch switch is part of the interlock circuit and WILL permit the engine to run with the seat empty provided the clutch/brake pedal is down. But since you connected the seat switch wires together, the clutch switch is the last switch to close and now it acts as though the seat is empty, even when the seat is actually occupied.