Dropping a grand large on the AK-20 cartridge from Traxxion Dynamics is not cheap. But neither is a crap front end that'll send you and your speed machine into the kitty litter at 90 mp/h. With regards to installation, you have two options here: you can send the forks to Traxxion in Atlanta to have the kit installed by the very knowledgeable people down there –or- you can spend a few bucks and get the tools from Traxxion to do it yourself. I chose the latter option, confident in the knowledge that, should I need a question answered, I could ring Traxxion and get a competent individual on the line to help me out. Your mileage may vary.
What You Need
Other than your forks and the AK-20 kit you'll need the following:
- Crescent wrenches (large and small)
- Box wrench
- Flat blade screwdriver
- Socket wrench with a hex-head tool
- Fork oil
- Fork seal grease
- Fork oil level measuring tool
- Fork spring compressor tool
- Fork oil bleed tool
- Fork cartridge installation tool
A clean, well-lit workbench with a vice will make life a lot easier too. This procedure will take about two hours to complete both forks. Obviously, the second tube will be done a lot quicker than the first based on the experience gained from the first fork completed.
Installation; How To
Prep the forks by removing them from the bike. Now, before doing ANYTHING else, make life a great deal easier by backing out all the suspension’s settings: compression, rebound and preload should all be reduced to full-out. All fork fluid should be removed and properly disposed of. This is done through removing the compression needle assembly at the bottom of the forks after the cap has been fully unscrewed. It helps to compress the forks a few times to get all the old fluid out. Make note of how nasty that stuff can get!
The author's particular forks came off a 2004 ZX-6RR and required some additional machining to be done on the compression needles. This was done to improve the precision of adjustability here as the blunt tips at the bottom of the BEFORE photo made the needles act more like an on/off switch as opposed to a full-range adjustment. Notice the pointed nature of the needles installed in their fittings after the work was done. This is much better where getting a precise feel from the front end is concerned. If you're working on the same forks as the author, you'll need a crescent wrench to complete remove/install the compression needle assemblies.
Not only were the compression needles machined, but the detent spring mechanism was removed by taking out the tiny balls and spring found in each assembly you see in the AFTER photo. From now on, the rider isn’t required to wait for the needles to click into position to get the feeling he is looking for. While having the compression needles machined may not be required with all forks, it’s an excellent idea to remove the detent spring mechanism, both at the rebound and compression ends. More fork fluid will be found when the compression needles are removed. Drain it all and clean the assembly.
Fork Cap Removal
Now that all the fluid has been drained from the forks, the fork caps (the part that houses the rebound and preload adjustments) must be removed. Again, backing all the suspension settings out as much as possible helps. A fork-spring compression tool, a box wrench and a second person will be needed for this task. Start by mounting the fork on a vice. Traxxion offers a fork vice (not cheap at almost $400) or buy their fork clamp kit. Either will be a necessary to get the work done without a great deal swearing.
Notice – the preload has been backed out all the way, making this job a little easier. Lower the collar of the fork compressor over the fork cap and position it around the spacer before installing the grip bars to it. Thread the grip bars through either side of the collar to the point that they fit themselves into the holes on either side of the spacer. Once this is solidly in position pull down on the compressor tool while the helper grasps the fork cap and holds it up. This will take significant force to accomplish. Once the nut below the fork cap is visible, have the helper slide the stopper in under it. If done right, everything should look like this:
Use a box wrench to loosen the jam-nut found below the fork cap and twist the fork cap off followed by removing the jam-nut. Pull the fork spring compressor tool off the spacer. Remove the spacer and the fork spring. Now remove the fork slider from the stanction. You should clean the fork slider. The author prefers to use ether because it's the cat's ass for removing any non-polar acetal (that means carbon-chain) substances from metal, like fork oil for example. When all is done, things should look something like this:
Cartridge Removal
Probably the most difficult task for the inexperienced suspension tuner, but not impossible without the proper tools. The cartridge installation tool and a hex-head socket wrench are required for this task. The cartridge installation tool is specific to a given brand of fork so two separate versions may be needed: one for removing the OE cartridge and the other for installing the AK-20 kit. When working with KYB forks, two separate cartridge installation tools will be needed.
DO NOT use an impact wrench to complete this task. It’s an excellent way to destroy the OE cartridge. A lot of local mechanics will offer to do this. Stay away, it’s dealerships trying to make a quick dollar. Save the cartridges along with everything removed from the forks. Traxxion has the ability to retrofit the AK-20 in pretty much any fork at a reasonable charge. Saving the OE cartridges is much less expensive than trying to obtain new OE interals for the forks converted.
Place the cartridge removal tool on the top of the OE cartridge as you insert the hex head socket up through the fork bottom. With the cartridge held secure from twisting with this tool, use the socket wrench to thread the bolt out from the fork bottom. When complete, an OE cartridge and a bolt will have been removed as shown below:
 
Be sure to remove any thread locking compound found on this bolt with a wire brush. Since the OE cartridge has been removed, cleaning inside the stanction is a good idea. Be sure to wipe down the cleaned surface as much as possible to prevent fork oil contamination. It cannot be stressed enough how important it is to have clean fork internals. Clean internals will make a world of difference in how well the suspension performs throughout its envelope and over time.
AK-20 Cartridge Installation
A fork installation tool and a hex head socket wrench are needed. It’s tricky to get the bolt threaded into the base of the AK-20 cartridge. Take the time to hit the mark. Firmly tighten the bolt with the new cartridge. DO NOT use any thread locking compound. At this point install the compression needle assembly at the bottom of the fork.
Fork Oil
Once again, Traxxion will have recommended the proper amount of fork oil based on the previously described factors. Have fork oil, fork oil measuring tool, fork seal grease and the cartridge bleeding tool ready. Place the fork in a vice in a manner as near to vertical as possible. This will aid in accurately reading the fork oil level. Install the slider over the stanction. This is done to prevent fork oil from leaking all over the deck. Fork oil level is always measured before the fork springs are installed. Again, this is done to get as precise a measurement as possible. Traxxion advised the author to fill the forks at 100mm from the top.
Use your intuition to ballpark this figure before using the fork oil level measuring tool. You will need to overshoot the recommended level to properly measure the oil level. Eyeball it initially.
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Once the cartridge damping rod has become completely submerged it is time to bleed it. Thread the fork bleed tool on to the damper rod as shown.
Fully depress/compress the damper rod until you feel a continuous, smooth force being generated from the cartridge while pushing up and down on it. This will indicate full removal of any air that would otherwise be found in the cartridge. It's also a good idea to move the slider over the stanction a few times to get as much oil between the two parts before final level measurement. Be careful not to raise the slider too much or risk earning a mess of oil to mop up.
After a sufficient amount of oil is in the fork, set the measuring tool to the proper length and place it on top of the fork as shown.
Fork Spring Installation
Have the fork bleed tool, a box wrench and a pipe cutter ready for this task. Traxxion will have recommended cutting the fork spring spacers to a specific length based on the type of fork, riding style and rider weight. In the author’s case - length was 100mm; your mileage may vary. Measure twice, cut once. It is a good idea to file the burrs on the cut surfaces to avoid contaminating fork oil which would otherwise increase wear on the internal valves.
The AK-20 kit comes with washers that must be placed on the spring buffer properly. It’s pretty easy to figure out where the two different washers go based on how they fit around the buffer itself. Use thy head here to get what’s seen on the fully assembled cartridge in the photo below:
The spring's lower washer and buffer must be threaded over the top of the cartridge. This is done via pulling the cartridge out of its fork oil bath with the fork bleeder tool, Remove the bleeder tool and slide the spring assembly over and down the damping rod. The rod itself won't move too much because the resistance created via the internal valving. Sliding the assembly on isn't difficult at all.
Once the spring assembly is installed, insert the jam-nut over the threaded portion of the damper rod as shown. Use the fork bleed tool to pull the cartridge up and install the jam-nut on the thread as shown. Surgical clamps are handy too.
Fork Cap Installation
Have a fork bleed tool, a box wrench, fork compressor tool and a helper ready in this job. Use the fork bleeder tool to pull the damper rod to full extension. Once this is done, put the spring spacer on. Use the spring compressor tool to apply the downforce needed to compress the spring/spacer assembly to the point where the helper can install the stopper tool between the spacer and the jam nut.
Once this is done, remove the fork bleed tool and thread the fork cap on to the damper rod. It is IMPERATIVE that the rebound adjustment on the fork cap is turned in three full turns. Thread the cap on so that the rebound adjuster is lightly snugged against the damper rod. Now use the jam-nut to prevent the fork cap from backing out once everything is assembled. Pay attention, DO NOT rotate the fork cap at all with respect to the damper rod while tightening the jam-nut against it.
Have the helper remove the stopper tool while lightly compressing the fork spring assembly. Once the stopper is removed, ease the spacer top against the bottom of the preload adjuster on the fork cap.
Final Assembly
Grab a large crescent wrench to mate the slider to the fork cap. Bring the slider up against the bottom of the fork cap and the twist the assembly together. Here we must ignore the manufacturer’s torque specification as the triple clamps will hold the cap in place when the forks are in situ. Hand-tighten the caps with the crescent wrench. This is done to provide easy access in the future should the need arise. Install the forks on the bike as per recommendations.
Conclusion
Being that the fork internals are completely new, it is important that the bike is set up properly to the rider’s weight. Set all the adjustments to Traxxion’s recommended spec and have the bike’s sag set to the rider’s needs. The AK-20 cartridges are merely a tool. They are a great aid in the set-up process via allowing a wider range of precise adjustment, greater consistency throughout the performance envelope, increased rider confidence and reduced lap times. As stated previously, one may phone Traxxion at any time should questions arise. Click on the link below for more information.
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