You can adjust the oil pump on most engines.
I am not sure where it is on your particular engine.
On my sled I just followed the cable down to where it fastens to the oil pump lever. There is a line scribed on the lever and one on the block, they should line up at an idle.
If it is stalling on you I would recommend you clean the carbs and do a tune up first before you start changing the oil pump settings.