Main Control Spring

Michaels Dad · Apr 24, 2018

3 Point on my 640 starting acting goofy when lifting today. Got all everything ready to pull the top cover off when I noticed 2 of the 3 bolts that hold the spring seat support were broken and the third was backed off and bent.
No problem getting them out.
Didn't have any grade 5 bolts here to replace them today, but I did have a grade 3 to play with. Noticed something, the original 3/8"NC bolt has an 11/16" head, new bolts will have a 5/8" head, shouldn't be any problem there.
Problem is can't get the 5/8" past the end of the spring.
Thoughts are, use Allen heads, going a small dip in the end of the spring to allow the head to pass, or remove the yoke and spring.
Manual doesn't cover this area, so I guess it unscrews. I think I remember someone trying to remove one a while back, but I can't find the post.
Any secrets to remove it without removing the cover to remove it?

TinCan · Apr 24, 2018

I had removed mine not long ago. I was advised not to, as it could wreck the threads. After awhile I looked at it. Hmm, I put a bar through the holes, and gave it a turn. It was not even tight at all, I just screwed it off. I only wanted to remove it to paint under it. Bought a new seal, and have not painted the back end yet, so it's still off.

Pat

Michaels Dad · Apr 24, 2018

I put a bar through the holes and tried very gently to unscrew it, kinda leary about putting to much on it for fear of breaking it off inside the housing.

sunbeam · Apr 24, 2018

Are you sure you are not looking at a 7/16 bolt.

JMOR · Apr 24, 2018

(quoted from post at 19:22:51 04/24/18) I put a bar through the holes and tried very gently to unscrew it, kinda leary about putting to much on it for fear of breaking it off inside the housing.

ise to be 'leary' here, because much torque and you will bend the internal linkage & lift adjustment becomes nightmare to impossible to get right!

riveroadrat · Apr 24, 2018

The yoke and spring unscrew but might be rusted up if they werent greased good or have never been off. You might need a blue wrench.

Dollar Bill · Apr 25, 2018

I put a bar through the holes and tried very gently to unscrew it, kinda leary about putting to much on it for fear of breaking it off inside the housing.

Sounds like rust has welded the two parts together - If it doesn't turn easily, heat the yoke red hot to break the rust bond and then let it to cool a bit before trying to turn as there is the tendency for it weld itself together if you try to turn it when both parts are red hot. If still no go, repeat the heat/cool cycle.

Liberally apply anti-seize during reassembly to allow adjustment and removal the next time. Put a new felt washer under it too.

Michaels Dad · Apr 25, 2018

(quoted from post at 19:43:09 04/24/18) Are you sure you are not looking at a 7/16 bolt.

Your'e right, 7/16"NC, two different sized heads though.

Main Control Spring

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TinCan

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riveroadrat

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Dollar Bill

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