I have a buddy that trashed the head on his 400S. He got a 400E head off of ebay. When installing it, I noticed a few things that are different, First is the carb intake is for a bigger carb???? Second, there is a hose on the intake that hangs down about 3 inches. I put the carb boot from the 400S on the head, as it tapered to fit the smaller carb. Tried to start it and nothing. I capped the hose on the intake and it started right up, but wont idle and is running rough. What is that hose?? The 400 S doesn't have it. And what about carb size?? Should we get the bigger carb or can we jet this one to work ?