Ok so I've been trying to get a bike running that has sat for about 2 yr. It's runs ok when on the throttle or choke but refuses to idle. It idles real rough but if I put a little choke it revs fine. So I was looking at my carbs and I noticed a couple cracked rubber caps covering a nipple on 3 of the carbs. One carb has a hose on the nipple that goes off to the fuel tank. My question is what is that hose and could the cracked caps affect the idle.