Gold Valve Emulators Review (GPZ900r) - Wrist Twisters
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Old 04-15-2018, 03:07 PM Thread Starter
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Gold Valve Emulators Review (GPZ900r)

Hello everyone,

This story starts at Max Speed Cycles in Kernersville, NC. The owner, Jim, has set up a lot of track bikes and is a suspension and tuning wizard. I asked him about front end conversions for my GPZ900r and he laughed. As a fellow dino-rocket enthusiast (his wife has a CB-1 and he has a VF1000 Interceptor along with a dozen other bikes) he said to install gold valve emulators and straight rate springs. He said KEEP THE BIKE STOCK (LOOKING). I was skeptical, but he promised with the right setup, the bike wouldn't be the limiting factor in the equation anymore lol.

The only problem with the equation is Kawasaki's AVDS (anti dive). To my surprise, the gold valve rendors that setup useless and installation was pretty straight forward when paired with new straight rate springs.

Since the GPZ is about 520lbs with fuel and 200lbs aboard, I opted for 0.95kg/mm Sonic Springs. Excellent quality for $97 shipped to my door. I asked Jim how to set up the gold valve and he said about 3 turns of preload on the gold valve (blue springs) and 15wt fork oil.

After all was said and done (cutting the preload spacers, 120mm fork oil level, fork seals, putting new o-rings throughout the anti dive unit and forks, drilling out the damper rods, etc.) the endeavor was close around $300. WORTH. EVERY. PENNY.

One test is to ride in the middle of the road and hit the reflectors. YOU NEVER FEEL THE REFLECTORS THROUGH THE BARS. The GPZ used to be so much rougher to ride than the 919, and now the GPZ is simply amazing. I can't get over how much of an improvement a properly tuned suspension is. Even with the 16" front wheel that is often cursed more than praised, the bike handles wonderfully. Now I'm researching how to get a better rear shock under the dino-rocket and really have a nice ride
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1965 PA-30 Twin Comanche
1985 Kawasaki GPZ900r
1999 Honda CBR1100XX
2005 Honda ST1300
2006 KLX250s
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Old 04-15-2018, 03:37 PM
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Thanks for posting this. I too have an old Kawasaki. GPZ 750 85. It's a project bike and the only thing really keeping it off the road is the suspension. The engine is solid. The fork seals have gone and it needs new upper tubes. I will replace everthing including the springs. The anti dive has me stumped. It's crap, even when new, so it's got to go. My plan was to fashion up some anti dive block off plates and replace the brake lines?
I'm also interested in what direction you go with in regards to the rear shock.
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Old 04-15-2018, 09:22 PM Thread Starter
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Originally Posted by Islandboy View Post
Thanks for posting this. I too have an old Kawasaki. GPZ 750 85. It's a project bike and the only thing really keeping it off the road is the suspension. The engine is solid. The fork seals have gone and it needs new upper tubes. I will replace everthing including the springs. The anti dive has me stumped. It's crap, even when new, so it's got to go. My plan was to fashion up some anti dive block off plates and replace the brake lines?
I'm also interested in what direction you go with in regards to the rear shock.
Definitely check out the Racetech website! It has the installation and emulator tuning guide. The biggest thing about the emulators is drilling the damper rods which I used a 1/8" drill bit to pilot then a harbor freight step drill to bore them out to 5/16". I also omitted the little cup at the bottom of the damper rod to ensure the fluid wasn't blocked or metered through the anti dive.

eBay seems to have the best prices on parts, and I highly recommend buying a metric o-ring kit but make sure you get Buna-N orings (or better) instead of the cheapo nitrile.

Here's a drawing I found for the block off plates. I pulled mine apart and gutted them internally and then staked/loctite 680'd the dowels in place so that the unit wouldn't do anything but looked completely stock. I robbed the braided lines off my 919 and put the stock rubber lines on the it. To my dismay, I had to use the left line off the 919 and install it from the master cylinder to the RH caliper on the GPZ since the GPZ forks are longer. Then I used a double banjo bolt on the RH caliper to attach the other braided line. It's on the to-do list to get longer brake lines.
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1965 PA-30 Twin Comanche
1985 Kawasaki GPZ900r
1999 Honda CBR1100XX
2005 Honda ST1300
2006 KLX250s
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Old 04-15-2018, 09:49 PM
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Quote:
Originally Posted by filipinoaviator View Post

I also omitted the little cup at the bottom of the damper rod to ensure the fluid wasn't blocked or metered through the anti dive.
That little cup is the hydraulic snubber to serve as the last gasp device to preclude a hard mechanical fork bottom out from occurring.
(same idea as the rubber like snubber ring on the rear shock that sits on the shaft right at the end face of the shock body)
They should NEVER be removed for a street fork build. ( a race build is another situation entirely)
If one is desperate for a few more mm of fork travel on bump, they can be trimmed down in height some, but not very much.
But why would someone doing street riding be so desperate for just a few more mm of travel on bump?

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Old 04-16-2018, 05:29 AM Thread Starter
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That little cup is the hydraulic snubber to serve as the last gasp device to preclude a hard mechanical fork bottom out from occurring.
(same idea as the rubber like snubber ring on the rear shock that sits on the shaft right at the end face of the shock body)
They should NEVER be removed for a street fork build. ( a race build is another situation entirely)
If one is desperate for a few more mm of fork travel on bump, they can be trimmed down in height some, but not very much.
But why would someone doing street riding be so desperate for just a few more mm of travel on bump?
Good to know, but with double the spring rate with springs that are shorter, it looks like the springs themselves will bottom out before the upper will crash into the lower. I omitted the little cup because it blocked off some of the holes that had been enlarged as part of the emulator setup as well as the cup redirected fluid flow through the anti dive.

Keep in mind this is a bike that won't be pushed hard or taken to a motocross track, nor will I wheelie this bike.
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1965 PA-30 Twin Comanche
1985 Kawasaki GPZ900r
1999 Honda CBR1100XX
2005 Honda ST1300
2006 KLX250s
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Old 04-16-2018, 07:08 AM
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I've heard nothing but good about the gold valves, however, I've always heard the progressive springs.

I had 16" tires on my CB700S, the selection was pretty limited and NO RADIALS. It didn't seem to have a problem in stock form handling the twisties.

I looked at one of those GPZ, damn hard to find even 10 years ago. Now the 700S is damn hard to find and even the 919s aren't very common.

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Old 04-16-2018, 07:48 PM
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Originally Posted by filipinoaviator View Post
Good to know, but with double the spring rate with springs that are shorter, it looks like the springs themselves will bottom out before the upper will crash into the lower.
I've never dealt with antidive forks but something doesn't ring right in my mind re the above.
I can't believe anyone would assemble a fork knowing there is full spring coil bind before the design bump stroke has been reached.
My guess is that your new shorter springs, once correctly internally preloaded by the correct spacer length, will not coil bind at all if they are linear springs, and will just have some coil bind if they are progressives.

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Old 04-17-2018, 09:52 PM Thread Starter
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Originally Posted by mcromo44 View Post
I've never dealt with antidive forks but something doesn't ring right in my mind re the above.
I can't believe anyone would assemble a fork knowing there is full spring coil bind before the design bump stroke has been reached.
My guess is that your new shorter springs, once correctly internally preloaded by the correct spacer length, will not coil bind at all if they are linear springs, and will just have some coil bind if they are progressives.
I can't believe anyone would bottom out the forks even after a botched wheelie. I can't believe I'm still posting to WristTwisters in 2018, yet here we are. There's really not a lot of information available about these goofy bikes, so I figured I'd share my personal results.

Time will tell as to whether or not the setup will perform as intended. So far, so good.

1965 PA-30 Twin Comanche
1985 Kawasaki GPZ900r
1999 Honda CBR1100XX
2005 Honda ST1300
2006 KLX250s
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Old 04-17-2018, 10:03 PM Thread Starter
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Originally Posted by KarlJay View Post
I've heard nothing but good about the gold valves, however, I've always heard the progressive springs.

I had 16" tires on my CB700S, the selection was pretty limited and NO RADIALS. It didn't seem to have a problem in stock form handling the twisties.

I looked at one of those GPZ, damn hard to find even 10 years ago. Now the 700S is damn hard to find and even the 919s aren't very common.
I've heard the arguments for and against the progressive springs. Jim told me that the straight rate springs are the way to go so that's what I ordered.

I also splurged on a set of Michelin Pilot Activ tires since they're offered in the oddball sizes. The guy that mounted the tires cussed them like something fierce but was interested to hear about how they handle since he only rides on Michelin tires as well.

And I agree, there aren't a crazy number of GPZs around. I had to drive 5 hours to Kentucky to get this one! I also had a difficult time finding parts until I came across a european website with the kawasaki oem part numbers that I could cross reference to ronayers... As it turns out, the GPZ900r shares a lot of parts with Concours 1000.

1965 PA-30 Twin Comanche
1985 Kawasaki GPZ900r
1999 Honda CBR1100XX
2005 Honda ST1300
2006 KLX250s
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Old 04-18-2018, 05:54 AM
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Quote:
Originally Posted by filipinoaviator View Post
I can't believe anyone would bottom out the forks even after a botched wheelie. I can't believe I'm still posting to WristTwisters in 2018, yet here we are. There's really not a lot of information available about these goofy bikes, so I figured I'd share my personal results.

Time will tell as to whether or not the setup will perform as intended. So far, so good.
You'd be surprised how easy it is to put a 919 into the hydraulic snubber range (the last bit of bump stroke travel) with the front brake, as my fork's max bump stroke indicator has attested to.

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Old 04-18-2018, 06:28 PM
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Keep us up in the loop with the Ninja 9's suspension mods. Still have mine that I purchased new in 85. Bone stock......Except for the 86 Ninja 1000 engine and carbs
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That'll work........
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Old 04-19-2018, 08:48 PM
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Yeah keep us posted. Cheers mate.

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