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:
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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.