I bought an old Craftman LT1000 with B&S motor 16.5 IC OHV. I already changed: oil, air filter, gas filter, battery, Start and carburetor. The motor start but after 15 sec approx turn off and I have to wait to start again the motor (crank but don't start). I already test with the fuel tank cap open or close, open holes in the muffler,.... Somebody can recommend something additionally to do?. Thanks in advance for the help.