If the three chains can't be tightened, you may have to remove a link to get them tightened properly. A loose chain could be causing your issues. Also, if you don't have a manual for the unit, I'd recommend getting one. I had tons of issues with my New Holland 499 Haybine, but after I got the manual and went through and adjusted everything properly, it now runs like clockwork. Don't discount the little things, as they can sometimes be the cause of many headaches. For instance, my Haybine kept plugging and slugging when cutting hay. I tried messing with reel speeds, reel position, tractor speeds, etc. Nothing helped. Then I replaced a few missing tines on the reel and it suddenly worked great. Could have saved myself hours of trouble had I just replaced them first.
'56 IH 350 Utility Gas, '47 Farmall H Gas, '08 Bobcat Toolcat 5600 Turbo
Pineray Dairy (RIP) -- 1880-2015 5 generations and 135 years of quality milk production
Stihl, Ariens, Tecumseh, LCT, Lauson, Kohler, Subaru and Lawn Boy Certified Technician with over 15 years experience.