Tractor Repair: NH65 square baler shearing flywheel bolts, shear bolts, knotter

Question
Hello Arnie,
Do you know the size bolt/strength necessary for the New Holland Compact 65 square baler? For some odd reason the plunger is hitting the plunger stop over and over again. It may not happen every other 200 bales, but it's starting to be very aggravating.
I trip the knotter and roll thru by hand and set the plunger stop to be out of the chamber after the knots have tied. This fixes it for a short while then it happens again.
Any ideas on whats happening?
Thanks,
Greg

Answer
  Hello,

  Don't use regular bolts, use genuine NH shear bolts for your model baler.  I think a 5/16" bolt about 1 and 3/4 inches long will fit, but it won't shear at the proper torque.  Genuine NH shear bolts are a special hardness designed to shear at the proper torque, and have a locknut so the nut will stay on without overtightening.  Be very careful with the plunger stop, if you set it wrong or make it so it doesn't work, you can break the needles off.  If it shears right after it ties a bale, the timing is a little late.  The most accurate way to time it is by tripping the knotter clutch, and turning the flywheel by hand until the tips of the needles just start to enter the bottom of the chamber.  The tips on the face of the plunger should be about even with the tips of the needles, or the plunger can be past the needles ( toward the rear of the baler) up to 3/4 inch.  If the plunger has gone back more than 3/4 inch past the tips of the needles, loosen the knotter drive chain, and jump the knotter clutch sprocket counter-clockwise 1 tooth.  Turn the flywheel backwards a little, put the needles back in their home position and repeat the procedure until you get it right.  Also check the knotter brake on the right end of the knotters.  If the brake pads are worn or the disk bolts are loose, the needles can work their way forward as you go over bumps in the field.  Since the needles hold the plunger stop out of the way, this can also cause bolts to shear.  The brake should be just tight enough to hold the needles from moving on their own.  Also make sure the flywheel is not loose on the baler. Good Luck,
    Arnie