I guess it starts clogging on the grass.. right? Anyway, what i suggest is that-
If you let the grass grow long it may choke up the mower even if you are only cutting 1/3. Try setting the deck on a higher setting to see if it goes better.
Make sure the underside of the mower deck is clean. If you have a mower that has a port to attach a hose for cleaning, use it to help keep the mower deck clean in between thorough cleanings.
Or otherwise, i would advice u refer to a help manual kind of thing if u have one. If not get it online, many are free, and the alternative to official manuals are usually found at reliable-store.com or u can simply get chilton/haynes ones if you're in for an expensive one.
let me know if this helps, or i'll try to find a good manual for u