Small engine rebuild help/question

I have an old cast iron techumseh engine I am trying to rebuild. (The rod broke). I am putting it back together. At the bottom of the stroke I can hear a sound and there seems to be some slight "play" where the rod does not move the poston any. I think the same at the top of the stroke.

Is this a problem or am I being overly cautious? This is my first rebuild and have learned alot but wanted to get your opinion. I have a video posted here:

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Reply to
stryped
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Hello:

It seems that:

1- Your videographer moved the camera, away from the bottom of the connecting rod, where it passes the lower part (Sump) of the block.

2- It may very well be that, you have the side cover removed, and therefore allowing crankshaft end play.

I would recommend that, you set the cam timing, and reinstall the side cover. Then rotate the engine. This is notwithstanding the fact, that I am assuming the engine is a 4 cycle?.

RK

Reply to
Refinish King

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

Rodan.

Reply to
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 detremental to the engine? This is on a tiller that is only used in the summers.

I appreciate your help!

Reply to
stryped

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.

Reply to
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

Reply to
golden oldie

if the free play you are talking about was that in the last few seconds of the video, that is WAY too much...

I have a piston and rod frmo a Techumseh engine sitting on my desk here. For real, it came out of my lawn mower a few years ago and i keep it here as a conversation piece.

The rod can slide __back and forth___ on the wrist pin and the wrist pin can slide __back and forth__ in the piston BUT there is NO free play at all that I can feel in my hand between the rod and piston in the ___UP / DOWN___ direction. If i understood what i saw in the video that you were turining the shaft several degrees back and forth without the piston moving, i would say something is very wrong.

Mark

Reply to
makolber

I couldnt tell anything from the video.

If there is excess slack in the wrist pin assembly, or in the main bearing, you will have to do something about it.. Otherwise, you are spending time and money on something that wont last.

It is easy enough to measure the crankshaft journal and the bearing ID and see how much play there is.

Same on wrist pin diameter and wrist pin bore, AND piston pin bore.

Measure first, then do what you have to do. You can use undersized crankshaft bearings if you have to. You can also buy a new piston or connecting rod, or you can usually remanufacture the ones you have.

Lots of ways around the problems, but putting it together too loose is a waste of time and money.

Reply to
HLS

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