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Racetech spring/emulator questions

gbw

gbw

Forum Mentor
Past Site Supporter
I'm about to install Racetech springs and cartridge emulators in the forks of my 77 GS750B. The instructions are pretty clear but leave out two details. Wondering if anyone here has done this and has an advice.

1. What is the correct spacer length?

The instructions provide a method to calculate the spacer length for a specific preload (I'm shooting for 20mm of preload). I'll do the calculations once I get the forks apart and take measurements. Wondering if anybody has done this and can give me a ball park figure for me to sanity check my calculations.

2. What is the correct oil level?

The instructions state to fill the forks to the correct level but then don't specify a specific level. I'll check with Racetech but wanted to see what others here have done.

Thanks for any help,
Greg
 
Racetech's web based Valving Search provided the following information. Does this jive with what others have done?

Emulator Valve Spring Preload: 3 turns (2 turns is how it is shipped from what I've read)

Fork Oil: OSFO 30 (30W?) Oil Level: 130 mm

Fork spring preload: 15 mm (I guess this is the length I need to cut the spacer)
 
Greg,

Any chance you have some pics of this project ? 30W oil sounds heavy to me.
 
bonanzadave said:
Greg,

Any chance you have some pics of this project ? 30W oil sounds heavy to me.
Click to expand...
I have not actually started this project yet but hope to get out in the garage a little today and have it finished sometime this weekend.

I wasn't planning on taking pics, but I could take some and post up a how-to (assuming I complete the job correctly :eek:)
 
bonanzadave said:
30W oil sounds heavy to me.
Click to expand...
30W oil also sounds heavy to every freekin' motorcycle shop in ChicagoLand and as a result no one carries it. Crap...one more thing to wait for. I was hoping to have the forks buttoned up before the clutch plates arrived.

Anyway, I confirmed with Racetech that 30W is indeed their recommendation for damper rod forks with their springs and emulators.

I was glad I talked to them as they gave me a short cut for determining the preload spacer length.
 
gbw said:
30W oil also sounds heavy to every freekin' motorcycle shop in ChicagoLand and as a result no one carries it. Crap...one more thing to wait for. I was hoping to have the forks buttoned up before the clutch plates arrived.

Anyway, I confirmed with Racetech that 30W is indeed their recommendation for damper rod forks with their springs and emulators.

I was glad I talked to them as they gave me a short cut for determining the preload spacer length.
Click to expand...

Does it have to be "fork" oil? How about regular 30W oil?
Also, did you try a Harley shop...seems I remember 30W fork oil back in Harley riding days....
 
30W will be way too heavy with emulators. ... 10W, 15W at most.

You probably want 2 turns on the springs.

:)
 
salty_monk said:
30W will be way too heavy with emulators. ... 10W, 15W at most.

You probably want 2 turns on the springs.

:)
Click to expand...
I asked Racetech again about the fork weight. They assure me in their experience with damper rod forks and emulators that 30W is the way to go. I'll give a try. Its easy to change to lower weight if I don't like it.

And Racetech says 3 turns on the blue spring. Again, I'll try that and adjust as necessary.

The one thing that bothers me is they don't make the perfect spring for 35mm forks. The springs they sent me are 26mm O.D. and do not fit in my fork. They are now sending me the next size down that are 23.5mm. My stock springs are 25mm O.D. so I'm concerned the 23.5mm springs will rattle around inside the tubes.

So, if after riding with 23.5mm springs doesn't work I'll return them and get some 25mm Sonic springs. I exchanged email with Sonic yesterday so I know they have them and they will work. It is good to have a backup plan :D

I'm so glad to be part of this forum. I have learned so much about suspension, Racetech, Sonic, emulators, etc from searching and reading. Thanks everyone for all the help.

Now if I could just find some stock fork caps I'd be sitting in butter!
 
Think I used Repsol 10 with my racetech emulators, 2 turns as Mr. salty monk suggested..a rep at racetech said the same thing when I called them.

Springs are progressive, with the tarozzi brace and all feels very nice.

Pretty sure I bought way too much fork oil, should still be some sitting around at Joe's custom speed shop possibly...enough to do another set at least.
 
Last edited:
Well, finally got the stator, clutch, and Racetech gear installed and took a short ride.

The front end feels firm, and I suspect I don't have enough SAG (too much preload), but it feels VERY good. The front would pogo a lot with the stock set up...that is gone.

A few of us are going for a little 4-day ride this weekend so I should have a feel for what adjustments to make when I get back.

Things I'm keeping my eye on:
Sag: I have about 20mm of preload. I might need to reduce this a little but should really measure the sag before I do anything.

Oil: Running 30W according to Racetech's recommendation. If the suspension feels too firm I'll drop this down the 15W or 20W and see if that changes things.

Thanks for all the help. Its good to have the bike all back together and running. Now if I could just sort out the charging system!!! But that is another thread. :)
 
Work out *how* it feels firm before you do the adjustments.

The Emulators split the Compression & rebound damping so you can adjust each independently.

Adjusting the Spring tension on the emulator adjusts compression damping only, changing oil weight primarily changes rebound damping only (you may have to compensate by adjusting spring tension on emulator slightly).

Too much compression damping can feel similar to too much preload with a harsh compression stroke so make sure you measure the sag.

Too much rebound damping will allow the fork to "pack down" (i.e. compress and not re-extend) - that's assuming that too much preload or too much compression damping aren't restricting it from compressing much at all.... :)

:)
 
I was surprised that Racetech says 30 weight, too.

On a similar sized bike (kawa zl900) with cartridge forks, I used Racetech's straight weight springs (not progressively wound) and the cartridge emulators. I ended up with 10 weight, which was their recommendation, and it worked out fine.

I would pay attention to what they said, you can always change it.
 
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