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KA24DE Idler Sprocket Fix


]2eDeYe

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It was pointed out to me that this info is really buried in my build thread so I decided I should start a thread just about this topic.

 

All of this is copied from my project thread and was done a while ago. It is still holding up just fine, but I don't put a whole ton of miles on this truck. I'd recommend using this rivet nut 94020A391 from mcmaster carr instead of the one in the first pictures. 

 

My original issue,  Timing chain jumped a tooth, but it still turns over and there are no bangs or clanks so I think I got lucky.

 

So I got into the timing chain. Found the problem....

IMG_3145.jpg

Idler bolt stripped the aluminum threads in the head. 

 

 

My buddy had the same thing happen to his ka. He did the same repair and it failed in a catastrophic manor. That bolt has a lot of force on it. I would at least put in a thread insert instead of a helicoil. Replacing the head is the only real way to fix it.

-Josh


Thanks for the jinx  :lol:


Look what I found.


a little fawked?

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Yup....

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Whut?

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Oh noes!!!

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hmmmm

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Shoulda been a clue, this is not VW tin goddammit!  :rofl:

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Peek....

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This is the next plan...maybe..more thinking is needed before ordering stuff.  :)

http://www.mcmaster.com/#standard-threaded-inserts/=iv7vm6

 

 

 

The threads were still decent for the helicoil, so I got creative with some epoxy....

Picked up some Marine Weld, basically JB Weld for wet conditions. Dabbed a bit on the helioil and threaded it in. Then I put the bolt in and let it cure for 24 hrs.


Better shot of that pesky oil passage.

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Epoxy, after some research into high temp and oil resistant epoxy I decided on this.

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Post cure

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I have an idler gear again.   :D

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At this point it was time to address the side loading that bolt is seeing. Here's how that went... pic heavy to tell the tale. 

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All back together. Runs awesome, no more rattle. I was able to torque the idler sprocket to spec, had to use a bit of jb weld on crush nut for the load screw, as it's not really designed for this application.   :lol:

 

IMG_5003.jpg

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I'd recommend using this rivet nut 94020A391 from mcmaster carr over the one I used in the previous pictures.

I'm still in shock that an engineer would design the idler sprocket hub in single shear while threaded into aluminum. Designed to fail...    :sick:

 

 

Tear down to replace the crushnut with a rivnut. 

 

IMG_8028_zpsa05777c1.jpg

 

 

I fixed the timing chain idler gear permanently with a one piece rivet nut. 

 

You can see here how the load bolt is centered on the idler bolt and applies pressure effectively putting the bolt in double shear instead of single shear. 

 

IMG_8029_zpsa9805e11.jpg

 

Old one two piece rivet nut

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New one piece rivet nut.

 

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and installed, was really easy with my press.

 

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Mostly back together. I will need to get a bit longer set screw so that I get a thread or two outside the jam nut. 

 

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This might seem a bit disjointed as it's mostly a copy paste from posts in my build thread.

 

build thread.

http://community.ratsun.net/topic/22191-1977-620-kingcab-deluxe/

 

 

I will probably go back through and clean it up a bit, but it's too damn hot to worry about that right now. :lol:

.

1399723_736940806352633_7466058867553376

 

 

A pic of this truck at Canby in 2014 :)

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Those were the days. :)

 

 

Edit: Did a little digging around and found that guys are using this bolt as a replacement for the stock one. The stock bolt is M12-1.25 X 100mm, this one is M12-1.25 X 110mm so it gives you a bit more thread engagement. You should be able to get one at any fastener store. 

 

http://www.mcmaster.com/#91180a721/=xvlo9v

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