OK, I need help, I have a Murray Select model 425600x8a with a Briggs&Stratton engine OHV 18.0 I/C. My first challenge was it did not wanted to start, I notice there was some gas mix with the oil so I change the oil, oil filter, spark plug, gas, gas cap (it was not closing all the way). After doing all of these changes still the mower starts but for just about 3 to 5 seconds. Any suggestion?

Hi,
It is either the carb is dirty and needs cleaning or the anti-backfire solenoid is not staying open. The first requires cleaning the carb fully and the latter is probably the key switch.
Peace,
Clarke
PS Your manual is here:
http://bsintek.basco.com/BriggsDocumentDisplay/default.aspx?filename=UekmAEVLnfBhU7y

Thank you, I will try then. I have had to turn it on by using a screw driver touching the solenoid, maybe I should just go and buy an new one. The carb I do not much about it so I will do some research on cleaning it, I do have carb cleaner I just hope I do not have to take it apart.