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I'm at a loss, need as much help as I can get here.


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#1 BillTheTractorMan OFFLINE  

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Posted September 14, 2011 - 03:10 PM

I broke down and decided I would find out what's up with knocker since people keep asking and the neighbor complained of the noise. Knocker knocks really loud, so loud the neighbor thought some one was beating on their door.

plowing the garden with the 1970 Sears suburban SS12 tractor - fall 2011 - YouTube

I've had it apart for two days now, yesterday it knocked only at TDC and not on the compression stroke. So I figured, valves. Pulled the head, and valve cover to find, yup, happens when the intake is closing and exhaust is opening and it's not a broken spring or in the valve cover.


Today, I checked for rod play/excess piston movement, which there is none. BUT there's no knock, no sound no nothing.


While running it has always knocked, how ever there was one time before that after a real tough mowing where it worked really hard it stopped knocking. the next day it was knocking again.


I can't figure it out, also it runs rich (black smoke occasionally and with 1/4 choke it will choke out) But there is white carbon build up. I was running farm grade fuel this summer while it was at the farm, but it only has 10% ethanol in it. At home I run 0% ethanol.


Any ideas?



Oh, it's a Tecumseh HH120.

#2 ducky OFFLINE  

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Posted September 14, 2011 - 03:17 PM

Bill I would bet on carbon buildup in the piston head area.
Decarbon and I will bet the knock goes away.

#3 mjodrey OFFLINE  

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Posted September 14, 2011 - 03:36 PM

Bill I would bet on carbon buildup in the piston head area.
Decarbon and I will bet the knock goes away.



Agreed,that is most likely what it is.

#4 BillTheTractorMan OFFLINE  

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Posted September 14, 2011 - 04:06 PM

it knocked with the head off yesterday. So the carbon is not the cause but it is getting cleaned up.

#5 caseguy OFFLINE  

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Posted September 14, 2011 - 04:18 PM

If it's still knocking with the head off, I would check for excessive slop at the wrist pin. If the rod works its way as far as it can go to one side, it may "bind" just enough to stop the knocking sound until the rod centers back up on the wrist pin. To inspect it thoroughly, you'll have to pull the piston though.

#6 olcowhand ONLINE  

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Posted September 14, 2011 - 04:26 PM

It sounds like possibly loose crank bearings. Check to see how much end to end play there is in the crank. You'll need to take all belts off the pulley to check this. If there is ANY end play, then you need to remove the shim gaskets & get all play removed without pre-loading the bearings.

Edited by Texas Deere and Horse, September 14, 2011 - 08:29 PM.


#7 Cvans OFFLINE  

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Posted September 14, 2011 - 05:12 PM

I've spent hundreds of dollars converting my gas tractors to diesel so they would sound like that and you get it for nothing.
Seriously I hope you get to the bottom of it. I tend to agree with Daniel on this one as it has to be some very substantial part of the engine to take that kind of beating without self destructing.

#8 DH1 ONLINE  

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Posted September 14, 2011 - 05:35 PM

It sounds like possibly loose crank bearings. Check to see how much end to end play there is in the crank. You'll need to take all belts off the pulley to check this. If there is ANY end play, then you need to remove the shim gaskets & get all play removed without pre-loading the braings.


:ditto: Definitely need to check this.

#9 Gtractor ONLINE  

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Posted September 14, 2011 - 06:11 PM

Does an HH120 have any syncronizing [sp] gears in the case? Just asking. I've heard some syncro gears stomp like a disco before, but they weren't in a Techumseh. :confuse:

#10 BillTheTractorMan OFFLINE  

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Posted September 14, 2011 - 06:16 PM

I'm thinking rod now... something there is not right.....

I have it all apart and the only thing not coming loose, is the rod from the crank. It turned but it wont separate. now that I have it open, I could hear it again.

#11 caseguy OFFLINE  

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Posted September 14, 2011 - 07:30 PM

Glad that you're getting to the bottom of the problem Bill! Hope you get it worked out soon!

#12 BillTheTractorMan OFFLINE  

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Posted September 14, 2011 - 07:54 PM

Rod is fine...


Light scoring on the crank and rod, no play in the wrist pin. I'm still thinking I should consider a new rod just to be sure? If I do replace it, do I have to replace the crank and wrist pin and piston too? this engine does not burn any oil.

#13 MH81 ONLINE  

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Posted September 14, 2011 - 08:25 PM

Are there any signs of the dipper hitting the wall or floor of the block? Is the dipper "peened" any on the end? The clearance isn't much and if the crank has play, the dipper could be hitting. They have a tapered end so they will just clear the bump on the wall.

#14 BillTheTractorMan OFFLINE  

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Posted September 14, 2011 - 08:47 PM

no damage to the dipper. crank has no play in it.

#15 Cvans OFFLINE  

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Posted September 14, 2011 - 08:49 PM

Mount the block to something substantial and try moving the ends of the crankshaft up and down, side to side, and in and out. You should feel little if any movement.




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