I also have that bolt on unit on my Kama. It may regulate oil pressure or it may just regulate the pressure at which the filter will bypass should it become clogged.
I just went back and looked at your overhaul pictures and the close up of your oil pump it would seem there is a pressure relief valve where the large cotter key is located. It will probably require shims under one end of the spring to adjust. However, if the pressure in the oil system is not getting high enough to open this valve it would do no good to shim as it only limits the max oil pressure.
Let us know what you find with the filter adjustment.
I just went back and looked at your overhaul pictures and the close up of your oil pump it would seem there is a pressure relief valve where the large cotter key is located. It will probably require shims under one end of the spring to adjust. However, if the pressure in the oil system is not getting high enough to open this valve it would do no good to shim as it only limits the max oil pressure.
Let us know what you find with the filter adjustment.