Small Engines (Lawn Mowers, etc.): B&S 5 hp no start, rover mower, air gap

Question
Hi, I have a B&S 5hp - mod. 130902, type 062501, code 79102406 on a "Rover Mower" brand chipper mod 95213.
Have been asked to try and get it started by an old bloke that says that it run out of petrol and now will not start.
Have adjusted the points and magneto gaps (20 thou and match book as air gap on magneto) and have good spark. It will not fire - even with fuel sprayed directly into the carby - it actually backfires through the carby, a lovely flame. The flywheel key (so I'm finding out from the owner) has been changed - the straight aluminium key in it at the moment has a '6' or possibly a '9' stamped into it. Is this the right key, or did they sometimes have a "stepped" key that would alter the timing? Am I on the right track? It has a carby that is mounted on the tank and all the diaphragms and pickups seem fine (sucking and blowing)and all the manifold seals etc. are good. It seems like timing to me.....thanks (an excellent forum by the way)

Answer
Brenton
If the timing is off you should get some kind of trying to start scenario. It may start and run crappy.Have you checked the points to see if the set is grounded? or in a good condition?Try doing a continuity on the points against the ground it shows a short you may have to unplug the points and follow tru on the wires