Small Engines (Lawn Mowers, etc.): starts up then dies, carburator, 2mo

Question
I have a craftman mower when I prime it it starts right up then dies out. I put in mew gas, cleaned the spark plug that is 5 mo. old. The mower was in the shop 5 mo. age due to varnish. Could it have varnish again? If so how can I fix it myself? The shop had it for 2mo. that is to long not to have your mower.

Thank you for any help you can give.
It is a craftman 6.75 hp rear drive modle# 917.377784

Answer
 Hello Greg:

 It is a Little Soon to be the Varnish in the Carburator again. It could be Trash/Water in the Carburator. If you want to Attempt to Clean the Carburator Yourself, Send me the Make, Model, Type and Code Numbers Off of the Engine and I May be Able to Locate a Breakdown of the Engine for you to View Online. This Breakdown will Assist you in Doing this Repair. Thanks.

 Respectfully

 John