How are you starting the ski? Pull the choke out till the ski fires. No throttle at all. I've seen lots of skis have an air leak at the water separator. I pressure up the fuel system with the lines blocked off close to the fuel baffle. I check everything... fuel valve function and holding pressure. You might try starting the ski on Reserve which may reveal a leak on the "ON" side.
It's a no no on this board but I use starting fluid when my skis have been sitting. One pop and off they go.
Sometimes I just have to show the can to the ski and they start right up.
I don't like grinding the starter or running down the battery. Good Luck !!