It depends on your terminology. You say you are good at kongs and want to improve the distance on your monkeys. If we want to speak by "definitions" then a monkey can be a slightly awkward vault because you are putting your hands on the rail before jumping. This drastically reduces your jump because instead of using your hands to correct your posture and give a slight extra push, you are using your hands as much as your feet to pull yourself through and push to give that extra distance.
With a kong, you run at your obstacle and dive into it (doesn't have to be a long dive, just enough to start to get your CoG (center of gravity) up into the air). There is a little area of take off specific to you that will give you maximum distance after your vault. Jump too close and you will crash into the obstacle. Too far away, and your CoG is coming down before you even get over the obstacle.
http://www.americanparkour.com/content/view/941/245/ That's Demon's Drill to making a more powerful kong. I haven't watched it in a while, but he should go over what I talked about here.