GS550: Sonic springs and emulators

[Scott S]

Somewhere along the way, I read a thread about using the Sonic springs and Gold Valve Emulators as a good upgrade for these bikes. I purchased the springs and emulators and then the project took a different direction.

I'd still like to use the springs and emulators in the stock forks. I'll use these on a different build. For the life of me, I can't find the thread that detailed the installation, with the instructions on drilling the holes, setting up the emulators, etc.
I can find several that talk about this, but I swear there was a thread that had lots of pics and a "how to".
Can someone walk me through this?

[Scott S]

There's this thread, but there's a lot of talk about the anti-dive forks, which the GS550 doesn't have. Is the install still pretty much the same?

https://www.thegsresources.com/_forum/showthread.php?250365-Sonic-Springs-and-Race-Tech-Emulators-intall&highlight=Emulators

[RichDesmond]

Somewhere along the way, I read a thread about using the Sonic springs and Gold Valve Emulators as a good upgrade for these bikes. I purchased the springs and emulators and then the project took a different direction.

I'd still like to use the springs and emulators in the stock forks. I'll use these on a different build. For the life of me, I can't find the thread that detailed the installation, with the instructions on drilling the holes, setting up the emulators, etc.
I can find several that talk about this, but I swear there was a thread that had lots of pics and a "how to".
Can someone walk me through this?

Installing the emulators is mostly the same set of procedures as changing the fork seals. Bunch of writeups and videos out there for that.
The big difference obviously is drilling the damper rods. I generally just enlarge the existing holes to 11mm (7/16") and start off with a fairly light setting on the emulator, 1.5 turns of preload on the screw. Be sure to clean up the drilled holes, the outside of the damper rod should be perfectly smooth.
Set the oil level to 120mm (details on that are in the Sonic Springs instruction) and also be sure to follow the Note A section of those instructions.
If you're doing this mods for performance reasons use 15w fork oil, if just making the ride more comfortable and controlled is the reason then 10w is better.

[Scott S]

Thanks Rich!
I've done fork seals before, and I have the Sonic instructions.
Do you just enlarge the existing holes? Or, do you add holes? Many of the threads I've seen add holes.

[cowboyup3371]

You enlarge the existing holes and make new ones. You'll get a set of instructions with the emulators that detail exactly what needs to be done; if you don't have them, here's a link to the ones that Mikes XS sells:

https://www.mikesxs.net/pdf/manuals/27-1086.pdf

[RichDesmond]

Thanks Rich!
I've done fork seals before, and I have the Sonic instructions.
Do you just enlarge the existing holes? Or, do you add holes? Many of the threads I've seen add holes.

The directions from Race-tech tell you to add holes. Sometimes that's fine, sometimes it's not.

The "it's not ok" case is a little hard to explain. First off, read this article from the Race-Tech site.

http://racetech.com/HTML_FILES/DampingRodForks.HTML

You need to understand how the oil moves between the chambers.

Then, look at Figure 3.8. Notice the "Rebound Check Valve". Now look at the rebound stroke section again, and Figure 3.12 and ask yourself what would happen if I drilled a big hole halfway between the compression holes and the rebound hole?
The answer is that when the fork is mostly compressed and the rebound check valve is below that new hole, the new hole acts as a very large rebound orifice and you have virtually no rebound damping until the fork extends enough for the check valve to pass above the hole.
This will happen if the new holes you drill are above the lowest point on the damper rod that the check valve passes over. There are some bikes, the SV650 being one, where that's exactly what happens if you follow Race-Tech's directions.

So, the bottom line is that if you're not sure, just enlarge the existing holes. That makes enough of a difference that the emulators still do what they are supposed to. If you are sure (and you can often tell by looking at the wear pattern on the damping rod) then go ahead and drill the new holes also.

[Scott S]

OK, next question....

I've rebuilt forks before, but not GS550E forks, specifically. This will be my first time inside them.
I see some people using/machining a spacer to fit on top of the damper rod. Do the emulators fit directly on top of the GS550 rods or is a spacer needed?

FWIW, I have the MikesXS emulators and they don't come with any type of spacer.