I’ve heard great things about these Race Tech Gold Valve Fork Emulators. What I have had trouble with, is getting the proper instal instructions and modifications needed for a 70’s BMW motorcycle.
Hopefully this will help others who plan to do the modification.
For information on how the emulators work, please read through this link.
Dampening Rod Forks and Emulators
For instructions and diagrams of a BMW /5 fork leg, check out an old Beemers and Bits link:
Unfortunately, I’m not going to test the results anytime soon. The bike is undergoing an entire rebuild and I’m at the point where i am trying to make a rolling chassis. So as i wait for some fork seals from BMW, I am starting to prep all the parts for reassembly.
With the dampening rods removed from the forks, they need to be disassembled and modified.
Here are both dampener rods and an old rod. You can see the difference in hole size to allow for more oil flow. Also note my gun cleaner and airbrush nozzle cleaners in the top of the photo. The inside of the rods and holes needs to be cleaned thoroughly after you drill them. Any small sharp bits of metal will chew up your fork seals, the inner fork tube walls, and all the other moving parts.
With the piston removed, a hole needs to be added to the top of the piston to allow more oil flow to the emulator. A lathe would probably be the best tool for the job but i had to improvise with my drill press. I found it easiest to drill from the inside. And i held the piston in place with a 13mm wrench. (My method may not be the safest or smartest but it worked for me. Be Safe!).
A Before and After of the piston top.
I have read some suggestions that say to cut the top of the piston off entirely, or to cut it where the holes are. I want to be able to tighten the piston on the dampener so I drilled a hole into it. This isn’t my photo but it give you an idea of another option:
In the end, i wound up shaving down the hex head of the piston a bit. i want to make sure that the part of the emulator that sticks down in the PVC spacer does not hit the piston. I also widened the piston holes to allow for more oil flow.
Then it was off to the local hardware store to buy some 3/4″ PVC to use as a spacer between the piston and the emulator. $.64 got me a foot of pipe. More then i’ll need.
It is suggested that you cut a length between 35-40mm. Since I didn’t cut the piston, i figured 40mm would be a safe size to keep distance between the piston and the emulator. After i squared up the ends, it was more like 39mm.
If you are using Race Tech springs as well, it is suggested that you add 15mm PVC spacers at the top of the springs. The Race Tech springs are slightly shorter then stock springs.
Here is a 15mm aluminum spacer next to my PVC spacers. The aluminum spacer was on one of the bikes when I disassembled it.
It is also recommended that you use use 15wt Fork Oil set to 130mm Oil Level (from top of fork tube to oil with the fork tube at bottom of stroke & the fork spring removed.)
I’ll be sure to post back once I feel the difference between my stock /5 forks and the forks on the rebuild bike.