Small Engines (Lawn Mowers, etc.): mower wont start, center fuel, lawn mower

Question
My kids pickup a free mower that wont start, what I have found is that if I dump gas in the carb it will start and remain running, but when we shut it down it won't restart agian unless we dump more gas in the carb each time, it seems to run fairly smoothly no sputtering just a bit off.

the mower is a poulan quattro lawn mower 4 hps

My kids want to use it for making money mowing lawns for the summer.

I appreciate any help you can give

Thanks Scott  

Answer
Hiya Scott-
1-Primer bulb is a likely suspect(if it has one)
2-If it has a fuel bowl(can't recall :P )the idle port in the center fuel tube that goes up into the carb may be dirt or clogged.
3-Always pays to install a new plug.

Try these items and get back to me ok?