Ich glaube Du musst
size=300x150
statt
width
nehmen...
http://code.google.com/apis/chart/#bar_charts
Bar chart size is handled in a different way than for other chart types. For horizontal bar charts of type bhs and bhg, and for vertical bar charts of type bvs and bvg, chart size is determined by the chs parameter. The chart is clipped (only partially visible) if the size specified (with chs) is too small. Because of this you may wish to specify bar width and spacing with chbh= <bar width in pixels>, <optional space between bars in a group>, <optional space between groups>