the nature of inline 4 engine is not balance.... if you do complete balancing also cannot, still need balance shaft no minimize the prob...Ok, so by this logic, if say the whole engine was completely balanced to the 3rd decimal point (just hypothetically speaking) would it still need this counter balance shaft? What vibration does it counter? Where is the vibration from?
you can read here to fully understand it...
Balance shaft - Wikipedia, the free encyclopedia@@AMEPARAM@@/wiki/File:Balanceshaft.jpg" class="image"><img alt="" src="http://upload.wikimedia.org/wikipedia/commons/thumb/8/84/Balanceshaft.jpg/250px-Balanceshaft.jpg"@@AMEPARAM@@commons/thumb/8/84/Balanceshaft.jpg/250px-Balanceshaft.jpg
http://www.autozine.org/technical_school/engine/smooth2.htm