On an S7D there is no distributor,just a magneto that the spark comes from,if you lay the plug on the head with the sparkplug wire connected to it,you should be able to see a spark jump the plug gap.If you don't have spark,which does sound likely,the first thing to do is clean and reset the points,they are in a little box under the carb near the bottom of the engine.If you take the cover off,you'll see the points,make sure they aren't oil soaked,that the points are shiny and the contact surface is flat,you can file them flat and shiny with an emory board.After your sure they are clean put them back in and set the gap to.020,then check your spark again.