my 1996 lft250 starts ok then after 5 to 8 seconds huge puffs of blue smoke from exhaust and then the engine stalls. any ideas what is the problem?

 

Well, pulling blue smoke usually means sucking oil so: A) You have a hole in your piston; B) You have too much oil in your crankcase; or C) You need a new exhaust valve, because the one you have is burned, allowing your oil to flow down the head onto the valve.