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990 Sickle Adjustment

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K

Kerwin

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I posted this in the implement alley forum, but thought I'd try here as well.

I'm trying to line up the sections and guards on an International 990 mower conditioner after putting on a new knife assembly, new guards, and new wear plates. I've found that that there is too much clearance in places between the sections and guards (about 1/16 in.). I would think to get the correct scissors action the clearance should be less.

So, do I need to shim the guards to close the gap with the section? Or does the cutter bar that everything mounts to need to be straightened somehow?

The operator's manual wants a 0.008 in. clearance between the hold down clips and the sections, so I don't want to pound the clips down and cause binding. The guards are forged and don't take readily to pounding for doing any adjustment.
 
I assume the answer is the same as it is for the older mowers. If so:

First, you need to check for big parts that are bent (like the cutter bar itself). This usually isn't the problem.
The top of the ledger plates in the guards should all be in line through the length of the cutter bar. IH had a gauge that rested on top of the cutter bar and the ledger plate to check position. But you can usually get a good idea by sighting down the tops of the plates. Bend the guards to adjust.

If the guards are all in line and the knife sections are in good shape, you can then check clearance between the sections and ledgers. You adjust the clearance by bending the hold down clips. They are supposed to be adjusted with a hammer. Hit the front of the clip to bend it down. Hit the middle of the clip to bend it up. Most of the time, my aim with a hammer isn't good enough to have much luck doing that adjustment.
 
If those are the new guards from CaseIH, they're hardened. Can't bend them one way or the other. You have to shim them up behind the bolt on the underside. The original guards are #484000R1. Very few places even have these anymore. Those guards are malleable & you can bend them to your whim. The new double guards may also be malleable. Webb's Sickle Service may have malleable single guards, too. If you can find a salvage yard with a few IH mowers, grab all the straight 484000R1's you can find. You can still get new ledger plates for them. I'll dig up the part number tomorrow, if you'd like.

Mike
 
Mike, the new guards that I put on are from Fleet Farm, forged and made in Germany. I tried pounding on one over the weekend and it didn't want to move much. As far as shimming, where is the best place to get shims?

Kerwin
 
As far as shimming, where is the best place to get shims?

Kerwin
Click to expand...
The side of an empty beer can 8).

Don't bother asking in an auto supply store. They don't know what shim stock is. Believe it or not, you will have better luck in a hobby store, where they sometimes have assorted metal stock for making models.
 
F&F has the hardened ones?! Shoot, I just had a couple of guys tell me that F&F was the last holdout for "soft" guards. Figures. My shims were made from leftover chimney flashing. F&F should have that in stock & not very expensive. I'm pretty sure the strips I cut were 1/2" x 3". If you find the knives to be tight after shimming, you may have to flip the wear plates (under the clips) over so the flange is pushing on the back of the knives themselves instead of the bar they're rivited to.

I still recommend finding originals, when you get time. Usually, all they need are new ledger plates. I'm slowly changing all of mine over to those as I find them. Ever so much easier to work with. Either way, if you have sharp knives & plates, knives are at the front of the guards, minimal clearence between knife & plate & everythings in register, you should be able to darn near cut lawn with it. I know I have. Not for the purpose of cutting the lawn with it mind you, just to see if it could & it does. If you have any more knife issues, give a holler on the grapevine here.

Mike
 
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