I have a ’96 400 xplorer which i recently rebuild after it dropped a bearing in the balancer shaft. she ran great for a while after the rebuild but now has real trouble idling before dying, it will then only fire back up if i give it some choke. when it runs it pulls clean all the way through the revs. I did adjust the idle screw but no change and checked the carb and manifold for air leaks, it seems good. any ideas?