I have a John Deere model L manure spreader. Has the Series 51 stamp on the front. Could use some help, or any advice anyone may have. The bottom "conveyor" chain that feeds the manure back towards the flippers spins continuously when the spreader is not loaded with the lever engaged or disengaged. But as soon as I load it and try to spread some manure with it, it will not move at all. I am not the original owner, and I do not have any of the literature, owner's/operator's manuals, parts catalog, or technical manual of any kind to find out if something is missing. Looks like all parts are there just cannot seem to connect the missing dot. Any advice, help, ideas where to find manuals, or any pointers in the right direction will be greatly appreciated! Thank you.