My freind put the battery on backwards and tried to crank it. Ralized the problem - got right battery - replaced the fuse. The mower cranks up and runs fine - but when you engage the pto - mower dies..... Craftsman 917.273642 18.5 hp 42"
#1 Make sure there are no more fuses first.
#2 I've seen a safety switch the problem. This could be under the seat. A quick way to diagnose this would be to unplug the switch and use a paper clip and put inside the plug to create a circuit. If this works replace the switch. Then again maybe it's just unplugged too.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix lawn mowers.