Complex sentence: To increase power you have to add cylinders, but when cylinders are added, the crankshaft has to be lengthened and after a very limited number of additions, the lengthened crankshaft begins to flex and vibrate all on its own.
Split into simpler sentences: To increase power you have to add cylinders, but when cylinders are added, the crankshaft has to be lengthened. After a very limited number of additions, the lengthened crankshaft begins to flex and vibrate all on its own.