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Engine Knock

tecumseh engine

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#1 kennye OFFLINE  

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Posted October 25, 2014 - 05:44 AM

1968?12 hp Tecumseh engine has loud knock......bearings on crank and connecting rod are good...valves all redone....engine still has a loud knock.  Not sure if crank is bad.  Will that cause the knocking?  Any suggestions would be appreciated.  Thanks



#2 BigFlash OFFLINE  

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Posted October 25, 2014 - 07:16 AM

Timing? on a lot of engine if the timing is off it can make for some pretty scary noises


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#3 olcowhand ONLINE  

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Posted October 25, 2014 - 08:07 AM

Bearings on crank can be good, but still knock bad if bearings aren't shimmed proper.  


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#4 Bruce Dorsi ONLINE  

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Posted October 25, 2014 - 09:22 AM

Loose flywheel?  ....Worn flywheel key?  .....Loose pulley/worn key on drive end of crankshaft?


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#5 DougT ONLINE  

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Posted October 25, 2014 - 10:16 AM

I haven't seen wrist pin or sloppy piston mentioned yet.


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#6 ol' stonebreaker ONLINE  

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Posted October 25, 2014 - 12:29 PM

  Maybe some plastigage is needed. 

                                         Mike


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#7 B10Dave OFFLINE  

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Posted October 25, 2014 - 06:58 PM

Carbon buildup in combustion chamber?


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#8 kennye OFFLINE  

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Posted October 26, 2014 - 06:10 AM

Thanks for the suggestions. Timing already checked out fine, engine runs good, except for extreme loud knocking. Knocking is so bad, engine seems like it is just going to fly apart.
Everything appears clean and in really good shape. Fly wheel seems to be tight, bearings are good, wrist pin and piston are also good.
Engine torn back down, connecting rod appears to be hitting side of crank. Connecting rod and fly wheel were replaced by previous owner. Could the rod be bent? Or could the crank bad?

#9 KennyP ONLINE  

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Posted October 26, 2014 - 06:43 AM

Where is it hitting the side of the crank?


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#10 kennye OFFLINE  

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Posted October 26, 2014 - 08:02 AM

The right side of crank
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#11 TAHOE ONLINE  

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Posted October 26, 2014 - 08:25 AM

If outside bearing cover had too thick of a gasket it can let the crank walk sideways causing a knock.

Also, I know my small block chevy rod has to be in only one directions, is rod in backwards? 

 

I was also going to suggest the a 10 hp head gasket on a 12, but sounds like you already found the crank issue. 


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#12 kennye OFFLINE  

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Posted October 27, 2014 - 05:12 AM

Thanks , I will check that out.

#13 kennye OFFLINE  

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Posted November 04, 2014 - 07:30 AM

Just wondering what this 1968 sears super ss12 not running would be worth?  Thinking of selling rather than fixing further.......There is a plough & an extra set of tires w/ rims.  Have $400 in tractor so far.



#14 MH81 ONLINE  

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Posted November 04, 2014 - 07:38 AM

Not running, you are on the high side of asking and probably well above actual.
Condition and location will determine the validity of that statement.
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#15 Cvans ONLINE  

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Posted November 04, 2014 - 01:53 PM

If delivery is included I will take it!  :smilewink:

If it looks nice and someone wants it bad enough your $400 will work. If your looking to unload it and It is in just average condition otherwise, you might be in for a bit of a struggle. Advertise it and see what happens. 


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