Originally Posted by Roger
There is no question about better clipping cover with my JD 717A, 7 Iron deck, with the deflector down, or partially down. I never run with it fully up (same as having taken it off).
In normal cutting (whatever that means), I run with it fully down. However, in heavy cutting (typically Spring, on very good lawns), clipping cover is a little better with the tip pulled up an inch or two. I use a light chain, and hook to make the adjustments (and to hold it in the full upright position for transport).
I use OEM high-lift blades, on cool weather grasses.
I work with forward/reverse passes, never racetrack. With the deflector off, the outcome is a good windrow at about 4 feet out. With the deflector fully down, some clippings are left in the first four feet, while others are thrown out to the 8 ft mark. With the deflector up, little debris is left in that first 4 ft. In the down position, the discharge force is more concentrated for further throw, but also will make the discharge path close to the ground, leaving some in that first 4 ft. With the deflector up, the discharge is much more of a spray, with too much force too high. In other words, the velocity vectors are scattered, rather than concentrated.
Maybe your cutting conditions are different. But, I consider it a mistake to take it off the 7 Iron deck.
I agree with your first post in that it makes a difference in which machine you have, and that you should try it both ways to see for yourself.
JD says the cover being down spreads the clippings more evenly. That all depends on the entire machine- blades, engine HP, width of deck etc etc.
I have owned a ton of JD's over the years. Some work better with the cover down, some do not.
MY Z720 (same as the OP's with bigger deck and engine) worked a little better with the deflector down. MY Z950 with the MOD deck works better with it off. The MOD has a side discharge cover built into the machine that raises and lowers depending on whether the MOD is open or closed, so it acts sort of like the deflector anyway. I tried it both with the deflector down and with it up before I finally took it off completely. Under normal circumstances, it made little difference, but if the clippings were longer, then having it in the up position was much better.
The point is, try it both ways and determine what's best on your lawns, with the blades you normally run (the OEM's on the 710's are std lift), then decide if you would be better off without it.
As far as it being able to deflect a stick or rock, I call BS on that, because I always left it down on my Z720 and I still threw several sticks quite a ways with it. Just as far as when I had it in the up position trying it to see how the clipping dispersal was.