Adjusting NH451 mower guards

[DogT]

New here. I've had this 451 for probably 10 years, I'll try to make it short. I've replaced the blades and guards on this mower for the second time now this spring. Trouble is I can't get the knife blades (sections) down on the guards. When I bend the guards up to meet the sections, only the tip of the sections meets the guard. I'm wondering if I need to remove some material off the guard mounting point to the bar so the guard sits up higher on the bar, thus meeting the sections properly or more nearly properly. I've never had it adjusted like the book shows it with the sections riding right on the guards flat. The inner plate (replaceable guard) does not meet the knife section by about 1/8", the outer one (on the end shoe) is good. Almost seems like the knife sections are riding too high in the guards.

Mostly run it at less than 540 PTO speed and in 4th gear (low range) on the JD2020 which is a bit slow. If I run it at 1st gear high range (5th gear) closer to PTO speed, it cuts fast but at my place it's a bit too fast unless I'm on a good area, Very hilly here and lots of trees and other items to get around and 5th gear is too fast sometimes.

I have to say this is the first year I've done much cutting in 5th gear and it's going real fast, but it also skips a lot. I've got about 20 acres and usually it takes me roughly 20 hours to do it in 4th gear, if I can do it in 5th gear it would probably cut that time in half which is nice, but I'd have to go around later and cut the hard areas at lower speed.

Anyhow, most interested in getting the sections meeting the guards better and any help there. I can supply pictures.

Many thanks, I did do a search, but didn't find much help there.

 

[DogT]

I'll answer my own question. Upon reading the manual, it says to bend the guards up until the front of the knife sections just meet the guard, so that's what I did. Then I also spent a couple hours getting the hold down clips adjusted to hold the knife sections down closer to the guard surface. That seems to have helped a lot, but it probably could be adjusted a bit more, but at least today I was mowing in 5th gear at about 5.5mph and it was cutting 4-5' grass without skipping or bogging. There's a few guards that tend to gather grass in the tip though, I'll have to mark them and see if I can adjust them a bit more, but 5 acres in an hour is not bad. I was running the rpm at 1800, that's below PTO speed by maybe 85% or about 450 rpm. 2100 rpm engine seems a bit fast on the hills in 5th, that's pushing it up about 6.5mph and 4th gear is less than 5mph at 2100. I've never cut this fast in the past without bogging up.