K161 vs K181 Piston Size?
 

Hi all,

I'm in the process of rebuilding the engine on my 73 which is a Kohler K161 7hp. I'm having a bit of a hard time finding a std size "k161" piston, although they are available, they fetch quite a bit more than a std K181 piston. Dont know why??

My question is, since both engines have the exact same bore size, and only differ by rod length, can I use a K181 8hp piston in my K161?

I have an old K181 piston and matched it up to my K161 piston, and they measure up perfectly(with digital calipers), even wrist pin location. I read a while back on another forum that a 8hp piston is a common replacement for the later 7hp engines, but I thought I would throw it out there to get some other opinions.

Thanks!

Jeff (teet)

You are correct, the 161 and the 181 had the same bore, 2.938". It was just the stroke that was different by .25". I believe that you are correct in thinking that you can use an 8 hp piston in a 7 hp motor. Now that I think of it I'm not sure they even make the shorter piston (161) any more.

Thanks Yosemite Sam, my reserach is leading me to believe its a possible swap as well. I guess theres only one way to find out :beer2:

Jeff (teet)

The motor in my 70 has a K181 piston in a K161 block. it has around 30 hours on it since it was rebuilt.

Sweet Merk! I thought I was hitting a dead end for a while! Did you use a Kohler brand piston, or aftermarket? Run ito any problems with the rebuild?

Thanks,

Jeff (teet)

I used only Kohler parts. Kohler parts do cost do cost a little more....the quality is better.....worth it in my book.
The 70 was used to help pay off a morgage. It was ran hard during the early years of it's life. I plan to work it some...not as hard as it was worked.
The motor throw a rod sometime in it's life. You could tell where the side of the block was repaired. The crank journal was still factory size. The only odd think I found was the cam lobe that opens the points had some major wear on it.
I replaced the following parts:
piston and rings
connecting rod
points plunger rod
valve guides
valves
head bolts
governor gear-it was a plastic one
gaskets and seals




The machine shop orders the parts for me. They have a good source plus they give me break ($$$) on parts.

Seems like the paint just dried.:biggrin2.gif: 30 hours... seems like alot.

I had the motor in another Cub that I sold. It is easier to have a motor that runs when you restore a tractor. One less problem to solve. The 70 has around 7 to 8 hours run time on it since it was restored.

i can get you a pretty decent price on your motor parts, www.cubclassics.com

Hi Chris, Thanks for the help. I measured my bore tonight with an actual bore gauge, and unfortunately I indeed have the 2-7/8" small bore K161. I am planning on trying to get it bored out to 2-15/16" which is the large bore K161 and K181 size. Do you have access to the old style 2-7/8" piston and rings? This is my dillema...they are very hard to find, and quite expensive once found.

Thanks,

Jeff (teet)