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Old Nov 3, 2012 | 03:32 PM
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TATONKA 96's Avatar
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Default evo knock
I have a 1996 flstc,has s.c. heads,cyls.not sure what other internal engine work done.but it has a knock when cold,after it warms up it goes away.any help is appreciated.
 
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Old Nov 3, 2012 | 04:59 PM
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Might be forged pistons.
 
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Old Nov 3, 2012 | 05:02 PM
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agreed, sounds like piston slap from forged pistons...
 
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Old Nov 3, 2012 | 06:33 PM
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What causes the slap with forged pistons? Installation method? What?
 
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Old Nov 3, 2012 | 06:48 PM
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Could be carbon build up too, Knocks until cylinders grow!! Of course it could also be something worse too, but hopefully it's one of the first two.
John
 
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Old Nov 3, 2012 | 07:15 PM
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Forged pistons generally require a little more cylinder bore clearance. Stock Harley's like my TC have very little clearance in the bore for an air cooled motor. One way they get away with it is they are so well designed with cylinders fins matched to allow cylinder to expand with piston. Piston is not round and only hits at Teflon patches. What I am wondering is is your's just a little loose and the knock really the noise of a loose piston slapping till piston expands to fit cylinder or is it too tight in bore making a piston pin or big pin on the crank knock? If it's the later (too tight) I would think you would see it when it cranks. I am just thinking out loud here. I do know from working on many a Toyota with lots of miles, a little too much clearance in a piston pin can make a lot of noise and I am talking only .001-.002 more then it should be.
 
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Old Nov 4, 2012 | 03:27 AM
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Is this really a knock, or could it be a lazy hydraulic tappet? Can you identify if it is top, mid or bottom of the engine?
 
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Old Nov 6, 2012 | 12:44 PM
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it sounds like its coming more from the top end.could it be a sticking lifter?
 
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Old Nov 7, 2012 | 03:35 PM
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They clatter rather than knock....could be a worn rocker maybe?
 
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