Combines Keep breaking sickle on 300 series

long time since I worked on a N series but here goes! Your wear plates in the first 2 or 3 feet out from the wobble box may be set too far forward. The wobble box arm moves in an arc so that the knife head and first couple of feet of the knife is well back towards the knife bar at the end of each stroke and well forward at mid stroke. The wear plates in the first 2 or 3 feet should be back against the knife bar to allow the knife to flex forward and back over a long distance during each stroke. With the wear plates forward, the knife has too flex in a very short distance and will break close to the knife head. A second point to look for is to check that as the arm moves through it's stroke it stays parallel and level with the knife bar through the full stroke. If the wobble box is not set up to do this the knife could be rising and falling each stroke by more than the depth of the slot in the gaurds thus bending the knife up and down over a very short distance each stroke. The wobble box mountings have to be shimmed if the arm does not swing true. The old AC jigs weren't always very accurate in some of these areas. Hope this helps. Cheers!

I'll bet the loose bearings are causing most of your problems. It doesn't take much slack to cause a lot of stress to the sickle bar. One way I have found besides visually looking at it is to open the cab door and run the header at full throttle. If you hear any clicking noise from the sickle drive, you have too much slack. When everything is up to snuff the header should run quite.

I'll bet the loose bearings are causing most of your problems. It doesn't take much slack to cause a lot of stress to the sickle bar. One way I have found besides visually looking at it is to open the cab door and run the combine at full throttle. If you hear any clicking noise from the sickle drive, you have too much slack. When everything is up to snuff the header should run quite.