Championship Kart Racing Engines
The series of engine block is determined by the height of the coil mount posts and the coil centering nib. Standard series have taller coil mounting posts and centering nib and the Super series have shorter ones.
McCulloch engineered the Super series block to bring the flywheel side bearing in closer to the centerline of the crank.
Start on the left side of the chart and review each of the positive ID features. Choose one of the features you think you have and move to the right column by column until you find a "Y". At the top of that column will be the model. Continue with the next feature on your block until you know what you have.
You should be able to identify exactly what model you have by using both charts. There is one exception for the standard series 91 and 91A where the difference between the two is port timing. The chart will be updated when I get more information on them.
It is possible to interchange blocks by shimming-up or cutting coil mount posts and nib to fit standard or super series side covers. This is why you can't always trust what the outside of an engine looks like to determine the model.