K161 rebuild questions

[Chevy_59 15]

  I've got a 702 that has been in the family since the eighties when we got it from the neighbor who bought it new. My dad had the engine rebuilt sometime in the late eighties when it was fogging the neighborhood while I mowed. It sat for quite a few years until I dug it out and got it running again in '21 for my boys. Last week they were driving it around  it started making "weird" noises so they shut it down and came and got me. We started it up and it sounded like it was severely knocking so we pulled it in the garage and this weekend we started tearing it down. It's been a leaker since we got it running again and I blamed myself for not double checking that they were checking the oil as it was low. After we got it off the tractor and removed the tin we went to remove the flywheel and found the nut was loose and the flywheel was wobbly. Wonder what the chances are that was our death noise and not the rod? It needs to come apart for a reseal anyway so we tore it down and inspected everything and checked clearances, that's where my question lies. The piston is marked .020 and the rod and crank measure out at -.010. The crank and rod look fine, no scoring or noticeable wear and when I measured them they come in at .034 clearance. The sources I have found don't agree with whether that is acceptable. The kohler manual I found says max is .035 but the garden tractor pulling tips website kohler section says .025. The bore looks decent, still has a good amount of crosshatch visible and the tractor didn't smoke or foul plugs, so think the rings were fine. 

  I'm wondering if it would seem foolish to re-gasket it and see if the flywheel was our death noise or if I should at least replace the rod? I'm hoping to get it back together as quick as we can, since we're hoping to get to the big show this year with it. (great timing, huh?) So I guess I'm mainly wondering what would you guys do in this situation? Thanks for reading and sorry so long.

[oliver2-44 9,731]

3 hours ago, Chevy_59 said:

The crank and rod look fine, no scoring or noticeable wear and when I measured them they come in at .034 clearance. The sources I have found don't agree with whether that is acceptable. The kohler manual I found says max is .035 but the garden tractor pulling tips website kohler section says .025. The

I suspecct you left a .0 of when you typed .034 as your measurement.  If that were correct it would knock very badly 

This chart in my copy of the Kohler manual shows rod to crank pin max wear limit at 0.0025.

 

[Chevy_59 15]

You are correct, my fingers got ahead of my brain and I forgot a zero. Also forgot to mention that upon measuring the piston and bore I apparently have one of the early K161's with the smaller bore.

[Achto 27,565]

If you pulled the piston out, I (as would the Kohler manual) would recommend re-scuffing the cylinder and replacing the rings.

 

As a rule of thumb rod to crank clearance on most engines is .001" per inch diameter of the crank pin. 1.5" crank pin = .0015" clearance. So .0034" clearance on your engine would seem extreme. Connecting rods that are .020" under are available should you decide to go that route.

[953 nut 55,188]

14 hours ago, Chevy_59 said:

The crank and rod look fine, no scoring or noticeable wear and when I measured them they come in at .034 clearance. The sources I have found don't agree with whether that is acceptable. The kohler manual I found says max is .035 but the garden tractor pulling tips website kohler section says .025

Did you use Plastigage for the crank measurement? In my opinion the Green Plastigage is the most accurate way to check rod/crank clearance.

[Chevy_59 15]

5 hours ago, Achto said:

If you pulled the piston out, I (as would the Kohler manual) would recommend re-scuffing the cylinder and replacing the rings.

 

As a rule of thumb rod to crank clearance on most engines is .001" per inch diameter of the crank pin. 1.5" crank pin = .0015" clearance. So .0034" clearance on your engine would seem extreme. Connecting rods that are .020" under are available should you decide to go that route.

Are rings still available for the small bore? most of the rebuild kits I'm finding say if you have a small bore engine to bore it and use a standard large bore piston/rings.

[Chevy_59 15]

3 hours ago, 953 nut said:

Did you use Plastigage for the crank measurement? In my opinion the Green Plastigage is the most accurate way to check rod/crank clearance.

i used a micrometer and telescoping gauges to measure, but i think i have some plastigauge around here somewhere that i could double check with.

[Achto 27,565]

46 minutes ago, Chevy_59 said:

Are rings still available for the small bore?

 

@WHX?? were you able to find the early small bore rings for your K161?

[ri702bill 8,316]

IMHO - boring an early small-bore block out to that of a STANDARD K181 bore has its advantages. PLENTY of STD pistons and ringsets are available. AND - it can be rebored later.......

[WHX?? 48,814]

1 hour ago, Achto said:

 

@WHX?? were you able to find the early small bore rings for your K161?

Yes I do believe I found them on flea bay... seller by the name of little red barn I think. I got std rings for a 321 build from them good seller.  The 161s small rings were std I recollect. No idea whether or not they would have the small bore .020 which is what Chevy needs. That might be a go fish. 

1 hour ago, ri702bill said:

IMHO - boring an early small-bore block out to that of a STANDARD K181 bore has its advantages. 

Agreed Bill but In my case the bore measured within small bore specs so our thoughts were to just put new cross hatch in and rings. Piston looked good so why go to the expense of boring to 181 for just the very occasional show cruzin with a trailer queen. We were just concerned with going away with the skeeter fogging. 

7 hours ago, Achto said:

If you pulled the piston out, I (as would the Kohler manual) would recommend re-scuffing the cylinder and replacing the rings.

Other ? Is Chev is does the piston show signs of oil washing? 

If not check the rod big end and if it passes new rings and chalk the noise up to the loose flywheel. 

You could go against the manual & use the old rings. Guys claimed they have with no issues. Personal decision I guess. 

[WHX?? 48,814]

Getting back to the loose flywheel triple check that bad boy carefully for cracks around the taper. It happens. Use a new key for sure & torque to spec. 

Off a 701 161 now a door stop. 

[Chevy_59 15]

1 hour ago, WHX?? said:

Other ? Is Chev is does the piston show signs of oil washing? 

If not check the rod big end and if it passes new rings and chalk the noise up to the loose flywheel. 

You could go against the manual & use the old rings. Guys claimed they have with no issues. Personal decision I guess. 

I don't think the piston or cylinder look too bad and like I said it wasn't smoking or fouling plugs. As far as the rod, like i said it looks fine and the crank looks great just was wondering about clearance. The older kohler manual i downloaded says .0035 max and the newer one that was referenced above says .0025 and I'm coming in at .0034. I'm just trying to decide about doing a close inspection on the flywheel and resealing the engine or if I should at least throw a new rod in it. I would rather hold off on a full rebuild with machine work until this winter so we can enjoy the tractor this summer.

 

[Chevy_59 15]

1 hour ago, WHX?? said:

Getting back to the loose flywheel triple check that bad boy carefully for cracks around the taper. It happens. Use a new key for sure & torque to spec. 

Off a 701 161 now a door stop. 

Definitely going to check that very closely, I think we have a crack detection kit at work so might take it in with me tomorrow.

[oliver2-44 9,731]

1 hour ago, Chevy_59 said:

I don't think the piston or cylinder look too bad and like I said it wasn't smoking or fouling plugs. As far as the rod, like i said it looks fine and the crank looks great just was wondering about clearance. The older kohler manual i downloaded says .0035 max and the newer one that was referenced above says .0025 and I'm coming in at .0034. I'm just trying to decide about doing a close inspection on the flywheel and resealing the engine or if I should at least throw a new rod in it. I would rather hold off on a full rebuild with machine work until this winter so we can enjoy the tractor this summer.

 

 

Based on the numbers your 0.034 is at the edge of the old kohler 0.0035 and  50% More out on the new kohler 0.0025 specs. 

So, where do your measurements point to the wear being? Crank big end , rod or both.  

By my way of thinking, if your going to mow with it all summer, if a new rod will reduce your clearance .001, it would be good insurance so an not to ventilate the block and have nothing usable left.   

[Chevy_59 15]

Ok, I checked the clearance with green plastigauge and it was just under .0020 about 2/3 of the way and .0015 towards the one end. I'm feeling ok about putting that back together and sending it. The big find right now is the flywheel is cracked by the keyway on the inside, so I guess I'm on the hunt for a replacement. 

12 minutes ago, oliver2-44 said:

Based on the numbers your 0.034 is at the edge of the old kohler 0.0035 and  50% More out on the new kohler 0.0025 specs. 

So, where do your measurements point to the wear being? Crank big end , rod or both.  

By my way of thinking, if your going to mow with it all summer, if a new rod will reduce your clearance .001, it would be good insurance so an not to ventilate the block and have nothing usable left.   

Not planning on heavy use, we do have a 32" mower I plan to put on so my boys can learn to mow like I did with it, but they won't be doing all the mowing with it. I have a newer Cub that handles that since we take care of a few yards. Mainly just gets used for cruising around and towing a little trailer with the neighborhood kids. 

[WHX?? 48,814]

3 hours ago, Chevy_59 said:

big find right now is the flywheel is cracked by the keyway on the inside

Crap I hope I didn't jinx ya. 

I got lucky  and found one on fleabay for 80 clams shipped.

 Seller said it was off a JD ...  

Correct Kohler PN is on my pic. 

 

I think you would be OK with that rod. 

[Chevy_59 15]

1 hour ago, WHX?? said:

Crap I hope I didn't jinx ya. 

I got lucky  and found one on fleabay for 80 clams shipped.

 Seller said it was off a JD ...  

Correct Kohler PN is on my pic. 

 

I think you would be OK with that rod. 

You didn't jinx me. I'm just a little upset with myself for not looking closely at it when removing it. I guess I was more interested in showing my boys how to disassemble the engine and thinking it was going to be the rod when I should have been thinking about why the flywheel nut would be loose.