I used to run a 260 with my air box lid on. Then I removed the lid and jumped to a 300. I have since had work done by here jugs racing and run a 330. The only time mine was hard to crank was when I was running albas needle. I went back with stock needle 3rd clip and bam first kick starts. Make sure you don't have your carb bowls mixed up. One has a little jet in the bottom, that's for the choke carb. Also make sure you don't have a air coming in around your carb boots. A leak down test can't find this because your carbs are off. The last thing I can think of is a weak stator.