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I’m working on my 1967 model 71 with the K161 engine and have been told that some of them used a smaller bore than the standard 2.9375 in. and those pistons are not available. I had planned to just put in rings but the set I ordered came for a much narrower ring groove. I used a snap gauge and can only measure my bore at 2.9320. I haven’t been able to find any other possible bore that it would be if it were the smaller bore. I’ve been told that if it is smaller I should order the piston for the larger bore and have the block bored to fit. Does anyone know what the smaller bore might be? Seems like mine is so close to the2.9375?
Thanks

It’s been a while, but as I recall the older smaller bore was 2-7/8 and the newer bore is 2-15/16. Try looking up a Original cub cadet and see if the pistons are the same numbers. There also may be a note in the parts listing for the different bore. A good “old” dealer should be able to help!

Thanks the 7/8 to 15/16 number should really help me. See I was only measuring my bore at about 5-6 1/1000 which makes me pretty sure I have the larger bore but I will keep investigating. Thanks again

White's in Canastota might be of help.

Yeah that’s right near home but we spend winters in Florida and this is a winter project. Thanks anyway!

I know very little about these small bore engines but from what I understand there is a difference in the piston pop up heights between the 2 7/8" and 2 15/16" bore engines. The correct beam length connecting rod must be used if I recall correctly. So base your parts research accordingly when replacing the entire assembly. The connecting rod is a wear and stress affected part and should be changed at that time.

Are you thinking that it’s not just as simple as ordering a rebuild kit for the larger bore and having the block bored? I hadn’t heard anything about the rod being different as well. This baby might become a rear ending transmission for somebody’s tractor puller if I keep getting discouraging news like that.
Thank you for the heads up so I will look closer at Rod length cause I’m ok with just buying a kit that I see on the net for only a little over 100 bucks but not to sure how much farther I will go.

Well, a complete rebuild kit would be the smart choice I think but firstly you have to be positive about what you have there. A K161 or a K181? Check to be sure that 161 is not really a 181. That is a very easy mistake to make when reading the tag.
Second, we need someone far better versed with these small block engines than I to chime in. That said I do recall reading some place that any 2 7/8" block can be bored to 2 15/16" without any bore wall thickness issues.
I myself are not a fan of any one third or one half rebuilds, as they usually end badly.
Your bore reading of 2.932, that makes no sense to me, can you verify that? 2.875 = 2 7/8". 2.937= 2 15/16", those I would think should be standard bore dimensions. Anybody?
Don't get discouraged diving in, rather remember that haste makes waste. Take a step back when things become confusing, and keep in mind that you don't need it today and tossing bills at it is no substitute for solid reasoning with a projected plan.
This one has the fenders and that single fact alone makes it worth bringing back up again. And yes, the base coat underneath is yellow. Also, the 71 is a fairly low numbers production machine making it much less common. Also, K241 ten Hp blocks are plentiful and easy enough to obtain and are a direct swap in but it would no longer be a 71 now would it?

My parts manual states the K161 as a recoil start engine for the 71, and the K181 as an electric start which yours obviously is.
I do not have a scanner so I'm attaching images for both engines as both are called for the 71 in my parts book. Perhaps you can find this information useful.

Tractorman50 wrote: ↑

Sat Dec 12, 2020 10:09 am

Yeah that’s right near home but we spend winters in Florida and this is a winter project. Thanks anyway!

Yeah, close to me too,LOL

You may find this helpful. Sorry about the crappy image quality, it's a monitor photo. My thinking is firstly you need to verify what you have there. The ID tag could possibly be from another engine, I have my doubts but verify all the same.
Engine stroke can be measured with a yardstick rotating the crank shaft from top center to bottom center, is it 2.500 or 2.750.
This would explain the piston pop up issue when people go about mixing up parts.

The outside of the blocks on the cam side are shaped different between the two. The K161 does not have any holes drilled in that area or flat bosses. These pics are with the kohler numbers
The K161 has most likley a 2 piece cam.
The whole manual can be viewed here. https://drive.google.com/file/d/1DOjyuM ... sp=sharing

You know I think the best info both of you are giving me is to STEP BACK! You guys are right. I don’t need it done right away and don’t need to just get in a hurry. I measured it today right up at the top of the cylinder today above where the ring stops and am very sure that it is a small bore. I’m going to sit tight for now. I’ll work on some paint sanding and paint for awhile. That’s a great point about using a bigger engine if I have too. After all I’m just in it for the fun anyway. Thanks you guys are awesome help!

I just glanced at EBay and was surprised at the listings for the K241. Didn’t realize it was the same one as the JD 112

link to service manual
Original Engine Service

link to parts manual
Kohler K-161

these manuals are actually right here on our own site. who knew?

small bore pistons 2 7/8"
41-874-01 std
41-874-02 .010
41-874-03 .020
41-874-04 .030

big bore pistons 2 15/16"
41-874-05 std
41-874-06 .010
41-874-07 .020
41-874-08 .030

Problem is the small bore pistons are hard to find and expensive. large bore ones are more common aftermarket also.
i would have to dig deep but i know you can punch out to the big bore. however i dont recall about the rod.

I have been calling all around central Florida to find a machine shop that still bores engine blocks. I haven’t had anything like that done for a long time but Seems like somebody must still do them.

Well i finally found an old stock piston and ring in standard size thanks the parts diagrams and part numbers from Dave c and ordered it from EBay. Thanks Guys! Now I'm going to replace axel seals and i will be looking to match seals and since i cant read the old ones.

Napa has them, ask for 9878.

Thanks Klapatta, I found them thru Case IH as they fit a corn head gearbox as well. I did try Napa by dimensions but didn’t have a number but I will remember that one. Thanks again

Routing new wire harness. I thought I would replace the mishmash that was on this model 71 but haven’t seen a diagram of the correct routing. Should the wires stay above the clutch cove and just go behind the generator? and strait forward to front grill or between the frame and engine?

The early narrow frames the wiring went over the clutch cover, I believe that was only for the 70/100’s.
All replacement harness I’ve seen have enough wire to run them through the frame next to the steering column, to the right of the clutch, under the flywheel starter, and then up the right side of the grill casting.

Thank you jmotuzick. It lays right in there and looks good. Thanks again