I am looking for some help with my '83 GS1100E fork setup using emulators

[oldGSfan]

I am 'mostly' happy with my forks except for one critical issue - sharp sudden impact compliance is not good.

• I have Sonic .95 springs, I weigh about 220.
• The oil level and preload is set per the Sonic instructions - from memory it's 150mm oil level from top, and the preload is per spec.
• 15W oil
• Anti-dive bypassed with plates (with passages), air holes at the top filled with J-B weld.
• The holes in the damper rod (?) are drilled out a bit larger by PO.

PO set it up with the anti-dive bypass, drilled out the damper rod, and put in emulators. All I did was clean, change oil and seals, and put in the new springs. And fiddle with adjustments.

They ride great in normal use but if I hit a sharp bump they feel like they have hydraulic lock and don't react well at all. When braking or riding normally they are compliant.

What I've done to try to improve things:

I reduced the oil level - I had it too high. Seems to me that too high oil level would introduce air springing which isn't really high impact resistance, but it was too stiff overall when initially set up, so it helped.

I also backed off the emulator adjuster nearly to the end, which also had a good effect. This is directly 'bypass' compliance adjustment, from what I can tell.

I had 20W and changed to 15W (mixed in some 10W to cut to half/half).

All I can think to do is reduce fork oil viscosity and use less until it's right. Edging the emulator back a turn may be possible but doesn't seem right. Not sure about the damper rod hole sizing, maybe enlarge more? It's close but no cigar, so any help would be appreciated. I am no fork setup expert, obviously - though I have rebuilt to stock many times, I've never dealt with mods.

[Rob S.]

I am 'mostly' happy with my forks except for one critical issue - sharp sudden impact compliance is not good.

• I have Sonic .95 springs, I weigh about 220.
• The oil level and preload is set per the Sonic instructions - from memory it's 150mm oil level from top, and the preload is per spec.
• 15W oil
• Anti-dive bypassed with plates (with passages), air holes at the top filled with J-B weld.
• The holes in the damper rod (?) are drilled out a bit larger by PO.

PO set it up with the anti-dive bypass, drilled out the damper rod, and put in emulators. All I did was clean, change oil and seals, and put in the new springs. And fiddle with adjustments.

They ride great in normal use but if I hit a sharp bump they feel like they have hydraulic lock and don't react well at all. When braking or riding normally they are compliant.

What I've done to try to improve things:

I reduced the oil level - I had it too high. Seems to me that too high oil level would introduce air springing which isn't really high impact resistance, but it was too stiff overall when initially set up, so it helped.

I also backed off the emulator adjuster nearly to the end, which also had a good effect. This is directly 'bypass' compliance adjustment, from what I can tell.

I had 20W and changed to 15W (mixed in some 10W to cut to half/half).

All I can think to do is reduce fork oil viscosity and use less until it's right. Edging the emulator back a turn may be possible but doesn't seem right. Not sure about the damper rod hole sizing, maybe enlarge more? It's close but no cigar, so any help would be appreciated. I am no fork setup expert, obviously - though I have rebuilt to stock many times, I've never dealt with mods.

Lose about 60 pounds.

Seriously, who advised you to go with .95 springs with 220 lbs in your riding boots?!?

Guessing the PO was on the petite side.

[Buffalo Bill]

I've been following your posts on this bike. You initially went all the way into a track setup, IMO.
Sharp initial shock, well that's what you get on bad pavement.
You might try swapping in your OEM progressive rate springs with the emulators to get another perspective. Then maybe buy new progressive rate springs.
Probably Bias Ply tires with their thick hard sidewalls contribute to the harshness. Radials have thin sidewalls.

I have 0.9 Sonic Springs in my 82 GS1100G, no emulators, Yes I feel the bad pavement in my wrists.
No discomfort in my 90 GSXF Katana with 1.0 Sonics. Newer design forks with 3 level adjustable rebound and radial tire..

[salty_monk]

If the emulators were installed properly your damper rod now has no effect on the compression damping as the Emulator controls that. The Oil weight will affect both compression (now managed by emulator) and the rebound (the small hole on the damper rod).

15W is likely too much. Even 12.5w might be too much at your weight. I would suggest 10w. Also note that 10w at one brand might not be the same as 10w at another (I know.. it's idiotic but that's the way it is) so it helps to pick a brand & stick to it if you're trying different things.

Put the lightest oil you can get away with for decent rebound. Adjust the emulator to suit to tune the compression damping. As it's an 83 doesn't it have adjustable rebound damping? My 83 did.... there were 1,2,3,4 setting that you rotated the nob too. I used to use 7.5w Maxima (at about 165lb) my springs were also lighter than yours..

Oil height can add some "air spring" but it won't be a big amount. The oil height will mostly add resistance to bottoming out the fork.

[oldGSfan]

OK I will try a 10W. I set it up per the Racetech calculator, street/intermediate/standard stiffness. It doesn't feel too stiff, it is only sharp impact that is the problem. Otherwise it is great. Lighter oil makes the most sense. I'm 6'3" or maybe 6'4" and have been this same weight for 40 years, losing 20 isn't gonna happen any time soon.

[first timer]

check your sag on the front forks all geared up, have a friend stabilize the bike while you sit on it. Your full weight on the bike the forks should sag about 25-30% of the total fork travel ( ie.100mm total travel then they should sink 25mm) if they sink more than that your spring rate is soft and you need stiffer springs or more preload, if less then that then they are to stiff.

Verify spring rate first then mess with oil weight and emulator compression settings. most cartridge forks run 5wt oil as a fyi. Try the 7.5wt maxima stuff or just some cheap ATF oil to see if it helps. ATF is close to 5wt, and good cheap alternative while you are screwing around.

Did your emulator kit come with extra shims? if so you can see if it has some thinner same od shims and try replacing some of the thicker shims in the compression stack with thinner shims. Just note the softer the compression stack the more front end dive you will get on front braking on the initial brake pull, which isn't great.

those sharp shocks you feel when you hit road heaves, cracked edges tar snakes ect, those are call high speed compressions. Aka the the fork shaft has suddenly accelerated at a very high speed to try and handle that sudden quick impact and the compression stack is trying to control that acceleration. Slow speed compression is more like when you are hitting a g-out or get a little air. That compression is a slower shaft acceleration. Those emulators probably don't separate out those differences to much but someone with skill can play with those shim stacks to created a valve curve that covers a little of both with the high speed being a little softer.

[KiwiAlfa156]

My Gold Valve Cartridge Emulators made with 3 extra sets of springs with different compression rates for larger tuning changes. The nut is more of a vernier adjustment of pre-load on the spring. There no shim stack on the 3 sets I've fitted and it's the valve spring and preload nut/screw that provides the same function.



The emulator replaces both compression and rebound damping. There is a slow speed damping circuit, which seems to be adjusted via oil viscosity, and the main valve which is a blow off valve adjusted by tension on the spring. This is to deal with the vČ hydraulic lock that stops standard damper rods from working when confronted with the high fork acceleration of a square edged bump.

Here's the Race Tech tuning guide https://racetech.com/emulator-tuning-guide/

My 750 Kat is fitted with the standard valve springs on the emulator and what ever the recommendation was for turns on the nut. There may have been a formula somewhere? Anyhow, they work great for me.

[oldGSfan]

I don't have those springs. Mine is OK for most conditions, but on a major sharp impact, like coming into a driveway where there's an inch or two curb, that jolt hits harder than it should. I am out of town, but when I get back in mid-July I will try lighter oil and be as careful as I can with measurement. In general, it is on the firm side, but not bad over normal road imperfections. I will check sag properly but for sure it's not as much as it should be. Like I said at the beginning, it is sharp sudden impacts like hitting a pothole at 30MPH that sends it right back through the bars. Nothing else is bothersome. Braking dive seems normal and controlled, cornering isn't twitchy or strange. Just those big impacts.

[salty_monk]

The emulator replaces both compression and rebound damping. /[/URL]

Not the case... The rebound is controlled by the original orifice in the piston. The Emulator only affects compression. That's why you need to set rebound first by selecting your oil weight.

This is from the guide you posted

Oil Viscosity

5wt - 30wt 15w typical by model

Oil viscosity is used to set rebound - the rate the suspension extends. This affects traction and stability. Heavier oil slows the rebound. Generally use the oil viscosity recommended on the DVS Setup Sheet. Once oil viscosity is selected the Emulator is used to set compression. The Emulator does not affect rebound. Oil viscosity varies by brand. Stick with the same brand if tuning rebound.

[KiwiAlfa156]

Not the case... The rebound is controlled by the original orifice in the piston. The Emulator only affects compression. That's why you need to set rebound first by selecting your oil weight.
;

I stand corrected, although the oil passes back through the emulator the check valve allows free passage of the oil to be metered by the rebound orifice. Which makes sense as the rebound extension speed is governed by the fork spring so is for all intents and purposes constant. No variation in vČ resistance so tuning through oil viscosity is a linear function. As the compression damping is varied independently through valve adjustment it's not viscosity dependent.