9660 sts grinding wet corn.

good luck with this problem our corn will be coming off at 30-35% not lookin farward to starting! we have problems with this almost every year. better have a cleaner at the elevator if your planing on storing it! the slow down kit and swept back wings on feed accelerater help a bit but it sill sucks in my opinion. someone on the site i'm sure will have the answers! good luck.

Do you have the seperator grate spacers in?

most crop damage is done in the feed accelerator. make sure that it is on low, also make sure that the feeder chain is on low.
we have had good luck removing all wear strip from the feed acc, and just running the wings. it is quite a job and you will have to put them back in if you plan on going back and forth between corn and beans.

Speaking of seperator grate spacers...can a guy leave them in for both corn and popcorn?

I would say yes, as both have grain to come off a cob

I'm trying to combine 30% corn with my 9870 and it is also grinding it up the corn, I'm going to try the grate spacer, but I'm having trouble either loading the hopper with small bits of cobs way too dirty! or I shovel it all out the back end! The only way I can keep the corn in is to have the top set at 26 and bottom at 16 with fan at 1300 and rotor at 300 with concave at 28. I had a JD tech with me and power shut down quite a few times and can't seem to get it set. Would it work to put on a row or two of grate covers to keep it going around the rotor or doesn't it work? I would really love some suggestions! 612C going 4mph 180-240bu corn

If cob is your problem, then DEFINELY put the spacers. If you have a JD tech with you and he has yet to suggest this, well...never mind.
Do the spacers and report back. Also FAST on slow speed and install swept back paddles when you get a chance, also install the perforated screens if you are getting docked or storing.