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amount of play in pony motor crankshaft

amount of play in pony motor crankshaft

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mikedell
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Friday I purchased a complete pony motor from a guy, and wanted to ask about crankshaft play.
The amount of play is nothing like my other one, but I can move the crankshaft a small amount when I pull on it. What amount of play is actually passable from operating? It doesn't look like it was leaking oil, but there is a small amount of play. It will eventually be rebuilt but I am wondering if as long as it's not leaking oil and the amount of play is minimal if I would be ok to use it as is for awhile?

Thanks guys
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Mon, May 12, 2014 12:45 AM
STEPHEN
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Mike, are you talking about end play or radial play?
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Mon, May 12, 2014 1:20 AM
ag-mike
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i think the book says few thousandths, i go by "less than 1/8"" ok 4 me. good luck.
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Mon, May 12, 2014 1:22 AM
Steve A
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Reply to ag-mike:
i think the book says few thousandths, i go by "less than 1/8"" ok 4 me. good luck.
When I got my D2 you could see the pony crank drifting back n forth when running, you could literally measure the endplay/thrust with a ruler, something near a 1/4 inch, It ran like a top but I feared self destruction so I opened it up, the dowel pin that held the bearing in place was laying in the bottom of the engine and the bearing was floating loose in the block. custom aluminum bearings were made
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Mon, May 12, 2014 1:35 AM
neil
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Reply to Steve A:
When I got my D2 you could see the pony crank drifting back n forth when running, you could literally measure the endplay/thrust with a ruler, something near a 1/4 inch, It ran like a top but I feared self destruction so I opened it up, the dowel pin that held the bearing in place was laying in the bottom of the engine and the bearing was floating loose in the block. custom aluminum bearings were made
I think maximum 25 thou. They're easy enough to fix so I figure why let it self-destruct. I put new bearings and dowels in mine and it's about 15 thou.
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Mon, May 12, 2014 2:25 AM
Mike Meyer
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Reply to Steve A:
When I got my D2 you could see the pony crank drifting back n forth when running, you could literally measure the endplay/thrust with a ruler, something near a 1/4 inch, It ran like a top but I feared self destruction so I opened it up, the dowel pin that held the bearing in place was laying in the bottom of the engine and the bearing was floating loose in the block. custom aluminum bearings were made


Who made your pilot motor bearings Steve and how much did they cost, I have a D2 / D4 pilot motor crankshaft here that had one main journal ground to 40 thou undersize and I've been wondering how to get a suitable bearing made.
Thanks
Mike
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Mon, May 12, 2014 4:17 AM
mikedell
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Reply to STEPHEN:
Mike, are you talking about end play or radial play?


Im talking about end play, I can grab the flywheel and move it around a little over 1/8 inch Im guessing.
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Mon, May 12, 2014 6:47 AM
Old Magnet
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Reply to mikedell:


Im talking about end play, I can grab the flywheel and move it around a little over 1/8 inch Im guessing.
Your pushing your luck, as stated 0.025" is the max. spec.
At 0.125" your pounding away on the thrust bearing dowel, if it hasn't dropped out already.
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Mon, May 12, 2014 6:53 AM
Steve A
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Reply to Old Magnet:
Your pushing your luck, as stated 0.025" is the max. spec.
At 0.125" your pounding away on the thrust bearing dowel, if it hasn't dropped out already.
Mike, I made the bearings on my south bend lathe, I am limited in my toolmaker skills and still managed to make the necessary bearings, the tough part was locating the dowel pin hole. If I remember there was a trial and a error or 2
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Mon, May 12, 2014 7:19 AM
mikedell
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Reply to Steve A:
Mike, I made the bearings on my south bend lathe, I am limited in my toolmaker skills and still managed to make the necessary bearings, the tough part was locating the dowel pin hole. If I remember there was a trial and a error or 2


I have a lathe, but have never really learned how to use it after having it for almost 5 years lol, maybe this would be a good time to actually use it.
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Mon, May 12, 2014 7:27 AM
neil
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Reply to mikedell:


I have a lathe, but have never really learned how to use it after having it for almost 5 years lol, maybe this would be a good time to actually use it.
Hi Mike,
any machine shop can make those bearings. They are just a simple unit turned on the OD (for a snug fit in the housing) and the ID (for the requisite clearance (maybe 010?) on the crank and then once you get them fitted up into the block and the crank in place, then you can drill the hole for the dowel so that your end play is within spec.
My guy made some out of that oil bronze material - material cost was negligible - just a bit of his time on the lathe. Or you can make them out of aluminum - either will work.
Or you can do like I did and buy them from Cat - I want to say 50 clams each?
Make sure you fit new dowels.
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Mon, May 12, 2014 7:20 PM
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