You probably should remove the knife bar for several reasons: Its a lot easier to change out the guard, you can inspect the knive condition and change any worn out or broken knives, you are less likely to cut yourself(fingers), you can inspect the knife bushing and you can then easily straighten the guards with a section of pipe so that they all line up. Just for curiosity sake, look in the cross tube to see if there is a spare knife hiding in there. You may have to remove a set bolt to get it out. To remove the cutter knife, park the pitman arm in the center of travel. The bolt head should be in view from the shoe hole. Use a socket and an open end or box wrench to back out the nut and bolt. (This is a special hardened bolt with a fine thread to keep from loosening). Pulling the knife out is sorta easy. Keep the blade level as you pull it out. Putting it in can be more difficult. Push the bar in slowly while raising up the bushing end so that the part of the knife entering the machine is parallel to the line of guards. If it jambs, chances are that a knife has slipped over a rock guard instead of through it. Just pull it out an inch and try again. Wear gloves to keep your fingers from getting cut.
Also check to see if the chevrons in the rubber rolls engage their partners. If not, remove the roll drive chain, put the rolls into proper register and reconnect the chain. Also inspect the belts. The reel drive belt is easy to change. The sickle drive belt is harder. I uncouple the driveline at the gearbox, unbolt the gearbox and remove the bearing retainer found underneath the case. This allows you to slip the belt on and off the drive pully when you pull the gearbox out of the side. While you are at it, inspect the bearing there and replace if dry or worn. To adjust the hold down clips, beat them down with a hammer (not too tight, though). There are some wear clips on the hold downs, too. Replace as necessary.
I like my machine to be just tight enough to not clack at all, but not so tight that the knife sticks. It should be easy to roll it over by hand. If you are using it for the first or last time in a season, slobber some old crankcase oil on the bar and guides.
These are easy to work on. Knives, rivets or bolts for knife replacement, reel teeth, bearings and guards can all be purchased at Tractor Supply. Buy a manual so you can set up the reel drive speed and skid shoe heights for your needs. Set the tire pressures and go to town.
While most have a hydraulic header lift (one way cylinder), its very convenient to add one for tongue swing. I run both circuits off of my loader connections. This makes it easy for road travel, getting close to a fence and getting through a gate.
