There were 2 versions of the K161 one was the "large bore" and the other the "small bore". The large bore takes the same piston as the k181, the small bore has the same bore size as the K141...my 73 has a small bore, and its hard to find oversize pistons for the small bore version...I dont know the measurements off hand, but it has been discussed here before, so a search might yield some results. A common fix for the small bore situation is to simply get it bored out to the k161-181 large bore size and throw in a k181 piston. Have you measured your bore?
http://www.onlycubcadets.net/forum/s...ead.php?t=1854
http://www.onlycubcadets.net/forum/s...ead.php?t=9193
Jeff (teet)