Small Engines (Lawn Mowers, etc.): Snowblower not throwing, power path, extension spring

Question
I have about a 20 year old Mastercraft blower (from Canadian Tire) with a Tecumseh engine. It won't throw the snow if it is more than a couple of inches of powder. The manual for replacing the belts just says "replace belt and reassemble" and doesn't mention how to tighten it. There is something shown in one diagram called an extension spring. Could that be useful? The auger seems to work okay, it's just the impeller (?) that stops.
Thanks.

Answer
Hi Ian,

You will need to trace the power path to see exactly where the the motion stops.  The belts are usually tensioned by an idler pulley which is spring tensioned.  The impeller may have a sheared key but you need to see what part is not turning, then inspect it in detail.  Use a helper to watch, while you operate the snowblower.

Let me know how you make out.
Michael