Re: Small engine rebuild help/question

On Jan 1, 12:31 am, "Rodan" <Ro...@xxxxxxxxxxx> wrote:
I am rebuilding an old cast iron Techumseh engine (The rod broke).
I am reassembling it, and at the bottom of the stroke I hear a sound.
Also at the top and bottom of the stroke there seems to be a slight
"play" where the rod does not move the piston any. Here is a video:
     http://www.youtube.com/watch?v=WG_kcd9VV3Q
Is this a problem or am I being overly cautious? This is my first
rebuild and I wanted to get your opinion.
      stryped.
___________________________________________________________________________­_

A worn or undersized wristpin would cause the noise and the sticking.
     Rodan.
____________________________________________________________________________

It is a 4 cycle. The cover is removed. I installed the cam and the noise
is less pronounced.         The noise is only at the bottom and top of
the stroke. Would an undersized wrist pin cause this? What sticking?
Will an undersized wrist pin be detrimental to the engine?   This is
on a tiller that is only used in the summers.
    stryped.
__________________________________________________________________________

A loose wrist pin will push the piston to the top of its stroke,
then leave the piston there until the moving wrist pin contacts
the bottom of its journal and begins to pull the piston down.
This makes the piston stay at the top of its stroke a short time
even though the wrist pin is moving down.    The same thing
happens at the bottom of the stroke.

The thumping may be the loose wrist pin banging against
the top and bottom if its journal as it is pushed up and down.

I have no guess regarding how long the engine will last if the
wrist pin is worn or undersized and not replaced.

Good luck.

Rodan.

If the wrist pin to piston clearance is enough to make a noise when
you are turning it over by hand I" would think it would be very easy
to see and feel when you have the pin in the piston in your hand. I
think that it won't last long while running before the thing self
destructs. It may be what you are hearing is the piston as it changes
direction.

chris
.

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