Andy, some pictures would help us with model indentification. This is partly because the Briggs site is currently not recognising that model number, which happens a lot.
If the engine blows blue smoke under load it is likely the rings are worn, but you can easily check this by feeling how much compression there is when you pull the starter, then putting a teaspoonful of oil in through the spark plug hole and pulling the starter again. If there is noticeably more compression with the oil in the cylinder, the compression ring is leaking. On Briggs engines, the compression ring is usually worn by the time the oil ring is. (Note this does not work with OHV Honda engines, which have chromed compression rings that easily outlast the oil rings.)
One of the reasons we need to see pictures of your engine is to try to establish whether it has a cast iron cylinder liner. It is best not to hone aluminium bores to remove glazing.
