Should I continue on the projects?
My bike is 1992 K75 RT, former Swedish police bike. I've been told, that at least some of the Police bikes had sport front suspension. My bike is equipped with 41 mm Showa fork. The fork caps do not have S-label and the forks only have one spring, length ca. 380 mm and on top ca 190 mm spacers. With this setup I only got about 20 mm sag when sitting on bike (75 kg) without fuel and all the fairings uninstalled. I didn't measure the sag with ful fuel tank and fairings, but I guess it could be around 30-40 mm. When I removed the fork top caps I measured the preload to be around 37 mm. The top edge of the cap is around 7 mm under the fork tube edge and when the circlip was released, it popped up ca. 30 mm above the fork tube edge.
The most confusing thing is, that the fork suspension travel of my bike is only ca. 120 mm. On regular fork it should be 185 mm. Has anyone measured the Showa fork springs and spacers? Are my 380 mm springs and 190 mm spacers standard? Sport forks should have two springs and 135 mm travel, so sport forks this is not. It seems to be so, that someone has made some changes to the fork for decreasing the suspension travel, or installed something wrong?
Hence, the sag with these 380 mm springs and 190 mm spacers was quite ok for the RT. But I'm going to strip my bike down to a Street tracker without the fairings, so quess I should have less preload for increasing the sag to normal for a lighter bike. I got a set of Progressive suspension fork springs on sale. They are about 445 mm long and came with 107 mm long spacers, so that would give me about 17 mm less preload than former setup.
I'm able to test ride my bike just on April, due the Finnish winter, but I hope getting the wheels from powder coating this week, so within a week or so I'm at least wiser about the sag with the new sprigns.
Finally, I flushed the forks today with petroleum and fill them up tomorrow with Motul 7,5 W fork oil to -170 mm before installing the springs. That should(?) be a standard setting, so it's a good starting poing.
Steering head bearings were in good condition, I just washed the old grease and dirt away with petroleum and regreased with CRC heavy duty MO2 grease.