The most common spot are the cylinder base gaskets, reed gaskets, carburetor boots, or the crank seals. If your Banshee starts up and idles then you can check the top end with just a can of starting fluid and spray around the cylinder base gaskets, around the reed gaskets and carburetor boots. The starting fluid will find the leak in those areas and with the engine idling it will let you know where the leak is. For the crank seals you will need to do a leak down test. You can go to YouTube South Texas Banshee and look for Banshee leak down test or you can contact him at SouthTexasBanshee.com he sells a leak down test kit or you can build your own with a few items that can be purchased at your local hardware store, Home Depot or Lowes.