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| Bought the machine used. Fan running about 690 and cylinder down to about 2 on the cylinder dial. Cylinder bars must really be worn to be down to 2 when it's suppose be between 8 and 16 sieve about three eights and chaffer about 3 fourth |
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Between Omaha and Des Moines, 7 miles South of I80 | Have you seen if your concave indicator, is at zero when the concave is closed (non-running)
 (JD 6620 concave adjust 001.JPG)
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 JD 6620 concave adjust 001.JPG (121KB - 119 downloads)
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southern Illinois | If you are not cracking/grinding beans close your concave more and close the bottom sieve a little to run them through again. If they are green pods you are about out of luck.
I had a 7720 and the setting for concaves were for bone dry beans, not dry beans with green pods in them. I ran it down towards wheat setting more than once to knock the beans out. |
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Between Omaha and Des Moines, 7 miles South of I80 | There is also a "rear" concave adjustment too. (non-running, and both sides) You have to look thru these "windows" and adjust the back of the concave. (I can't quote the procedure without an operators manual, in front of me)
 (JD 6620 concave adjust 003.jpg)
 (JD 6620 concave adjust 002.JPG)
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JD 6620 concave adjust 003.jpg (130KB - 121 downloads)
JD 6620 concave adjust 002.JPG (113KB - 140 downloads)
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North Central Kentucky | +1 It seems like concave and sieve was always tighter than book recommends. |
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| speed the cylinder up to 900.
nedpepper |
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Barton Co. Missouri | Like suggested above close bottom sieve more always had to run more return than wanted to get clean beans. |
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w/c Illinois | I always had to run my 6620 concave way tight as well. Usually ran beans on the wheat setting and corn on the bean setting. Stop the machine loaded and look at the crop on top of the walkers. You may be running un-thrashed pods out the straw chopper as well. |
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SW MN | +1 and crank concave tighter till you start cracking the beans. Speed fan up to wide open |
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SW Minnesota | Back when we had a 7720 we quit trying to get the sieves set just right to get most of the pods out. You would have a different variety or different conditions the next day and you would start monkeying around with it all over again. We got a round-hole bean sieve and not hardly a pod in the tank after that. |
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| Pay no attention to that decal on there. Always ran lots tighter than it says. Corn also. |
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Stewart, MN | I had the same problem last year. Turned out to be a few rows of "fingers" gone off the chaffer or sieve don't remember wich one |
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Coles County, Illinois | Like stated by 4WD the Zero indicator is adjustable so with the thresher stopped crank the concave all the way up and adjust the indicator to read zero. Next take a 1/4" bolt and place it between the ribs of the rasp bars. The ribs should extend out further than the bolt. Concave wear could be a factor as well. They tend to wear more in the center. With standard bars, I replace the concave every other time it gets new bars.
Pulling the chaffer out is pretty quick if you have a helper. Just two 5/16" bolts hold it in place. I pull mine out every year after I'm done and inspect for bent fingers, cracks or damage. Pulling the sieve is just a little harder. You have to remove the two angle brackets that supports the chaffer and then there's a 1/2" bolt on each side in the front that holds it in place. The angle brackets can be used on either side so take a look at them before you remove them so you get the bolts back in the proper holes.
With all the above done you should have an idea of the condition of the threshing and cleaning condition of the machine. I don't have my manual with me but the mid point of the recommended range is a good starting point. If I remember correctly the front chaffer is 9/16", rear 3/4" and the sieve is 7/16". I run my fan around 800 rpm.
Now it's time to determine the crop conditions. I start out with the concave set at 8 and cylinder speed @ 500. I load the machine up. My no load thresher engaged speed is 2390 rpm. I pull the rpms down to 2340 and disengage the thresher under full load. I then go back and look down in the hatch above the straw walkers. Ideally you want intact stems with all the pods still attached but the pods all threshed open. With completely ripe beans this should be possible by just adjusting the concave.
What makes things difficult is when you have green beans, green stems and most difficult green pods. This year, I have all three with loads testing 10.8. My beans did not rippen evenly. The rains we are still getting will help this but I didn't need the >3" so far. Hopefully when it drys up all beans will be ripe. I'm about 1/2 done.
Green beans with Yellow pods normally will just require tightening the concave to thresh although at some point you'll start losing the threshed pods off the stems. When I see that happening and I still have unthreshed pods, I consider increasing cylinder speed up to 600 rpm. High cylinder speed increases the chance for cracking the beans so you have to watch the grain tank for this.
When I've got the concave and cylinder speed set. I consider sieve and (rarely) chaffer adjustments away from the recommended mid point. This would normally only be in reaction to pods in the tank. Conditions throughout the field will vary and in difficult conditions (green pods with low moisture tests/ shatter loss) one has to start making compromises. If I close the sieve I'll get alot more return, reduced capacity and a slightly cleaner sample. The green pods in the tank are pretty flat so I've decided I could sell some but Thursday they got above my level of acceptability so I quit cutting around 3 pm and decided to wait. I spent the rest of the afternoon cleaning the machine up |
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| Thanks for all the great ideals guys. |
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ecmn | make sure the concave and bars are straight, I was having issues with the 8820 and found two bars bent bad from a bigger rock. used a bottle jack and straightened them out and problem fixed. |
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6620 pods in the grain tank
