Hi Bill,
I once put a heap of very wet stuff (wet palms I think) into the machine and it turned it into mush, which I then had to clean out. Nowadays, I usually let stuff dry out for a few days before putting them through. At one stage a stick got caught in the feed chute and wedged itself tight so that the fan belt could not drive the flywheel. By the time I realised what was happening, the fan belt was burnt through so I put in the replacement. Otherwise it has taken anything I can throw at it including 7.5cm branches through the chute. The engine is B&S, which is absolutely up to the task (I take the neighbours branches & greens as well!). Hope that helps.
cheers
darryll

Darryll, Just want to thank you again for your answer. Motor is replaced with a 6.5hp and my mulcher is now fantastic! The motor was $140 brand new including postage. Took about 1hr to remove the old one and put the new one on. Then things got ugly. Removing the rusted on pulley from the old motor took 8hrs despite an overnight soak in WD40. Just needed a final adjustment of the motor position to get good belt tension and it was working. New motor is dead easy to start and destroys whatever goes into the chute.

I think it cost me $950 all up, that is with $100 transport cost to Brisbane. I've done a couple of oil changes, replaced a belt (it came with a spare) and it is still munching through mine & two neighbour's backyard detritus.