So I was wondering yalls opinion on this. I need to run the engine it's a Kohler 16hp k series and after measuring the crankshaft, it is out of spec to a point I should probably source another one. Mine has a spot just after top dead center that is worn. My question is the scoring on this rod looks bad, but will this cause it to break?
Connecting rod scoring
- Thread starter Fordiesel69
- Start date
Get it resized or buy another.
the soft aluminum rod wore the steel crank?
I don't think it will break right away unless there is significant play and it is knocking, but with that said its days are numbered with that kind of scoring. Those rods aren't super expensive, I wouldn't put it back together without replacing the rod personally.
What kind of application was this engine used for?
It is a 16hp Kohler k341 tractor engine. Kohler kept the same crank pin diameter from 12hp up to 18hp OHV k361. The crank pin will normally wear directly on the surface where TDC is and shortly after. Usually nowhere else unless it was neglected. This is a high hour engine in need of a proper rebuild however being the crank pin is not scored I just need to run it this season while I source the rebuild parts. I also do not have machine shops anywhere local that can do cranks.
Just remove any aluminum transfer from the crank pin and install a new connecting rod. If there is some light scoring on the crank pin you can polish it lightly with very fine emery cloth. While you are at it, re-ring the piston and hone the cylinder. I have personally repaired engines this way that lasted many years afterwards.
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So now that I have a computer and keyboard to type on instead of a phone here is the dilema. To do this engine properly, it will need bored to .010 over and I need to find a crankshaft that is within spec, and then find a rod to match to it. That will take some time.
To use the engine as is, it would be best for me re-use this rod, as the exisiting rod and crank is already shot. There is no machining on it, its already worn close to if not at .010 over spec and if you turn it to .020 the hardness will be gone.
So based on the scoring present, if I polish the crank with crocus cloth, and polish the rod, will the pounding just be a noise issue or will it just snap? If just noise / knock, I dont care.
To use the engine as is, it would be best for me re-use this rod, as the exisiting rod and crank is already shot. There is no machining on it, its already worn close to if not at .010 over spec and if you turn it to .020 the hardness will be gone.
So based on the scoring present, if I polish the crank with crocus cloth, and polish the rod, will the pounding just be a noise issue or will it just snap? If just noise / knock, I dont care.
I think you could lightly polish the crank, replace the rod, and it stands a good chance of giving a couple of years before it gets to this point again. If the rod is not expensive, that’s what I would do, and run a heavy weight oil in it.
Replace the rod. It is not salvageable.
That was going to be my suggestion too. Change the rod, polish the crank. The crank does not look (to me) all that bad.
I don't think the rod has a special treatment for the bearing surface, so the rod could probably be re-sized. That's done by machining the rod cap surfaces where they bolt together to reduce the size of the bore, then assembling and boring the hole to spec. Heck, it can even be done by hand, if one has the skills. But why? A replacement rod can't be expensive.
Likely a good idea to use higher viscosity oil due to a small amount of extra rod bearing clearance. Suggestion: M1 15W-50.
But using the existing parts might be a big risk, as the knocking you talk about will likely worsen until catastrophic failure.
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Crocus cloth ! if its the real stuff, it is basically a cloth impregnated with jewelers' rouge, that is an ultra fine polishing compound.
It would take years to remove the stuck or galled aluminum from the crankshaft crank pin using that. Just saying.
It may work in your case as the pin doesn't look too bad.
crocus cloth,
1. a layer of jeweler's rouge on thick cloth backing, used for polishing metals and jewels.
I learned about it from my machinist dad back in the mid 50's.
Ebay has Kohler overhaul kits available for cheap. I went through a 14 horse on a Gravely, I am quite satisfied. Oversize/undersized are available also.
UPDATE:
So the issue is, the rod to crank journal clearance is 0.002 preffered, and at 0.0035 (which is three and a half thousands) is the limit. Mine has a spot in it, only around the TDC that is about 0.008 ~ 0.010 (eight to ten thousands). So the crank is egg shaped as the engine has never been "burned up", but rather it is a high hour engine 1800 hrs. Kohler uses the same crankpin diameter on 10HP up to 18HP K361 rare ohv version. I frankly think this was a mistake as the 10HP and 12HP versions can last forever with proper maint. The 14HP thru 18HP see to all develop rod knock as I think the crank is undersized for the load.
Anyways, I found an affordable replacement crankshaft, and as long as it measures out correctly, I should be good to buy a new rod. Will keep y'all informed.
So the issue is, the rod to crank journal clearance is 0.002 preffered, and at 0.0035 (which is three and a half thousands) is the limit. Mine has a spot in it, only around the TDC that is about 0.008 ~ 0.010 (eight to ten thousands). So the crank is egg shaped as the engine has never been "burned up", but rather it is a high hour engine 1800 hrs. Kohler uses the same crankpin diameter on 10HP up to 18HP K361 rare ohv version. I frankly think this was a mistake as the 10HP and 12HP versions can last forever with proper maint. The 14HP thru 18HP see to all develop rod knock as I think the crank is undersized for the load.
Anyways, I found an affordable replacement crankshaft, and as long as it measures out correctly, I should be good to buy a new rod. Will keep y'all informed.
