Hey
when looking for a clog, there are a few areas you can check. First of all, as a few people suggested, you can remove the screws under the headlights, and look in the suction inlet for a clog, and fish it out if you see one. Second, as also suggested, open the clean-out port on the back side above the handle realease/below the hose, and again check for a clog. Make sure to partially recline the vacuum or you may not see a clog in the base. FInally, there is a small clear window on the backside of the Cyclone XT, where the dirt enters the collection bin area. Check that for a clog, and if there is one, turn the machine around and pull it out through the opening where the dirt enters the bin.
I have a PDF of the Cyclone XT manual, I will email it to you!