K1200RS Transmission Drain Plug Seal
By James Pellenbarg
April 1998
The problem is slow leakage from the transmission drain plug. There is no washer of any kind. The surfaces of the plug and the case are machined with small ridges that are supposed to fit together perfectly to provide a seal. Unfortunately, they didn’t seal on my bike.
The dealer was ready to replace the transmission as they had no answers. Before to transplantation, I spent the time chasing after O-rings of various sizes to find one to fill the space between the bottom threads (on the case) and the base of the drain plug. I settled on a #14 O-ring (15/16″ OD x 3/4″ ID x 3/32″).
This has proven over the last two months & over 600 miles to have corrected the problem. The bike was ridden on several occasions at speeds slow enough to cause the fans to operate. It was at these elevated temps that previous attempts would fail.
I believe that this information may be of value to anyone out there who may at some point experience similar problems with washerless drain plugs.