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Saving A Crankshaft (maybe)


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#1 coldone OFFLINE  

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Posted April 21, 2013 - 08:48 PM

I am working on rebuilding "Jumping JaKK". Its the K341 that had the front of the snapper 1650 jumping around. Sometime it had sheared the flywheel key, unknown to me, and I kept trying to figure out why it was jumping all over the place. Well I guess I am the one to boogger up the crankshaft taper. It has many deep scores in it where the key ate it up. The fly wheel too. Everything I read said that I was screwed and needed a new crank and fly wheel. Yall know me, if its broke I cant make it much more broke by trying something.

 

So here is what I am trying. I have filled all the score marks with braze. I will file down the heavy stuff, then I will use lapping compound to finish it up. I will use JB weld in the fly wheel to fix the score marks in it and use the lapping to fit it to the crank.

 

My preliminary test indicated that it was a go on the crank. I hit a few of the divots with braze, let it cool, and lapped it in with the fly wheel. I had nice even marks on everything.  The braze wore away nicely and I had fit on all surfaces, no file marks were left from taking the heavy stuff off.

 

After that, I fired up the torch and hit the few other places that needed it. Its out in the shop waiting for me to have some time to go through the process again.

 

My biggest concern will be warpage. I heated evenly and cooled slowly. I have no way to really test it until I put it in the block. Then I can use a Dial indicator to see what TIR looks like.

 

 

I aint puttin alot of faith in this, I think its gonna be warpped bad. So I hope somebody here has a crank and fly wheel that they will part with when this doesnt work out.

 

I will get pics of the process when I have time to go out and work on it. Hopefully sometime this week.


  • MH81 said thank you

#2 chris m OFFLINE  

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Posted April 21, 2013 - 09:00 PM

First off good luck! It sounds to me like it may work. How are the key ways on both? If they are ok, I think this fix will work for you.

I'll be looking forward to the pictures and updates. :thumbs:



#3 Deck_Drive OFFLINE  

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Posted April 21, 2013 - 09:01 PM

I have "almost" the same issue. My big briggs 16 chewed up the fly wheel and crank shaft keyways. I am thinking of drilling a hole directly through the crank and into the flywheel, then drive a grade 8 pin, or bolt, to keep it firing correctly. Now, I have pretty much given up all hope of fixing it correctly because I dont want to pay 300 bucks for a new crank and who knows what for a new fly wheel.

Do you think this would work?



#4 Arti OFFLINE  

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Posted April 21, 2013 - 09:32 PM

I think you might be in luck with this fix.. Brazing wouldn't get it as hot as welding on it, Good luck on it keep us posted.



#5 marlboro180 OFFLINE  

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Posted April 21, 2013 - 09:34 PM

I say why not give it a try, just like have you done. Nothing lost, nothing gained. Let us know how it works out, or fails miserably. ( I vote for the former ) :D :thumbs:



#6 KennyP ONLINE  

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Posted April 22, 2013 - 05:57 AM

Sounds like a well thought out fix. Good luck with it. Just keep an eye on the flywheel nut as time passes so it stays tight.



#7 coldone OFFLINE  

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Posted April 22, 2013 - 07:20 PM

No time for it today. maybe tomorrow.



#8 Moosetales OFFLINE  

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Posted April 24, 2013 - 01:57 AM

My preliminary test indicated that it was a go on the crank. I hit a few of the divots with braze, let it cool, and lapped it in with the fly wheel. I had nice even marks on everything.  The braze wore away nicely and I had fit on all surfaces, no file marks were left from taking the heavy stuff off.

 

My biggest concern will be warpage. I heated evenly and cooled slowly. I have no way to really test it until I put it in the block. Then I can use a Dial indicator to see what TIR looks like.

 

TIR? and Lapped? These are new terms to me. Thanks.



#9 coldone OFFLINE  

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Posted April 24, 2013 - 05:28 AM

Lapping, in this case, is where you use an abrasive compound between two pieces and it "fits" them to each other. Lapping valves, lapping surfaces, lapping flywheel to crank.

 

TIR is Total run out, how much wobble is in the end of a shaft when spun. Not out of round but off center.



#10 HowardsMF155 ONLINE  

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Posted April 24, 2013 - 05:31 AM

TIR? and Lapped? These are new terms to me. Thanks.

Total Indicated Runnout=TIR.  

 

Ask Wikipedia for more infor:  http://en.wikipedia....dicator_reading



#11 coldone OFFLINE  

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Posted April 25, 2013 - 08:10 PM

Got a chance to check the runout. 0.003 inches. I think we have a winner!

 

Now just got to get the valve seats cut and put it back together.


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