spray some starting fluid or brake cleaner up through the carbs towards the pistons and then see if it will light off. Let us know what happens. Dont worry about a leak down test yet, you just need to know the 3 basics right now. Compression, Spark, fuel! If you spray carb clean up there and it doesn't light off, then you need to check compression. If the compression is ok then check to see if the flywheel is installed right, or if the flywheel key is sheared.