evo knock

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Nov 3, 2012 | 03:32 PM

TATONKA 96

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Intermediate

Joined: Oct 2011

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From: MS.

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.

Nov 3, 2012 | 04:59 PM

Spanners39

Seasoned HDF Member

Joined: Dec 2010

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From: Coromandel Peninsula New Zealand

Might be forged pistons.

Nov 3, 2012 | 05:02 PM

Gigawitz

Road Captain

Joined: Sep 2007

Posts: 525

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From: San Diego

agreed, sounds like piston slap from forged pistons...

Nov 3, 2012 | 06:33 PM

HarleyReece

Cruiser

Joined: Mar 2010

Posts: 237

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What causes the slap with forged pistons? Installation method? What?

Nov 3, 2012 | 06:48 PM

miacycles

Elite HDF Member

Joined: Sep 2007

Posts: 4,468

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From: Bluffton, South Carolina

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

Nov 3, 2012 | 07:15 PM

Jackie Paper

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From: Honah Lee

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.