This is a HOW-TO on changing out fork springs on the CBR1000RR.
Background: The big daddy RR has some of the best forks seen yet on any production motorcycle, much less another Honda sportbike. From the Honda website: "43.0mm inverted HMAS cartridge fork with spring-preload, rebound and compression-damping adjustability; 4.7-inch travel". Sounds pretty common, and is very similar to the forks on the RC51, sans about 0.4" of travel. So what is it that makes this fork so special? Thanks to Peter Verdone for the following information regarding the internal valving: Two stage high speed damping, with all 0.10mm shims on the first stage, all 0.15mm shims on the second, but the stages overlap only in the middle, not at the end (if they truly overlap at all). Rebound is HMAS. Compression is high flow. Rebound valve is 4 port, compression are 3 port.
Even with all this high tech stuff that you can't see, Honda still decided to fit relatively soft 0.85kg/mm (as measured by Racetech) springs in the forks. Getting correct sag numbers on the bike is near impossible if you are a typical American male. I weigh in at 220# and I was able to manage about 40mm of sag with the preload adjusters all the way in. Your goal for static sag (bike + rider) is 25-30mm for the track, and 30-35mm for the street. The first step in setting up suspension correctly is setting sag. In order to get correct sag, you need the correct springs and Traxxion Dynamics, Ohlins, and Racetech all sell aftermarket springs for about $110. I got my 1.0 kg/mm Racetech springs as a super deal off ebay.
To determine proper spring rate, Traxxion has provided us with the following graph:
Tools:
6mm allen wrench
adjustable wrench
12mm combination wrench
sockets with extensions
large 1-1/4" socket
thin safety wire or equivalent
metric tapemeasure
pipe cutter
sandpaper
drill and drill bits
and clean rags
Procedure:
Before we begin I must stress the importance of working in a VERY clean environment. Even very small particles of dirt getting in the forks will wind up in your valve stacks and is ultimately a major pain in the ass to clean out. It requires COMPLETE disassembly of the forks. Be clean!
The first thing you need to do is back out the preload and rebound all the way to get as much pressure off the springs as possible. It also helps in other ways that will be apparent later. Next, use a front stand that mounts in the steering stem to get the front of the bike off the ground. I don't have one of that type so I decided to be creative.
Now that all the weight is off the front, begin by removing the small clip that retains the preload adjuster nut.
Now remove the preload adjuster nut.
Remove the small O-ring on the preload adjuster.
Carefully loosen the smaller locknut with the adjustable wrench. I would have loved to use a combination wrench but no standard or metric wrench will fit this nut. It is about 18-1/2mm. Notice how I ground down the face of the wrench to make it thinner. You may need to do this in order to get your 12mm wrench on the flats of the preload adjuster later.
Remove the locknut.
Now loosen the upper triple clamp and clip-on using the 6mm allen wrench. You may need to loosen the clutch lever to get at the fasteners. Carefully loosen the fork cap. It may be tight! Move the forks full left lock against the steering stop when you do this.
Remove the fork cap, long spacer (spring collar), and short spacer (joint collar). SLOWLY remove the stock fork spring while turning it like it's a screw. This will allow most of the oil to drain off the spring. The damping rod will likely slide slowly down into the fork. Use a needle nose pliers to grab it and pull it back up.
Tie a 12 inch piece of lockwire around the damping rod where the o-ring was.
This is the stock spacer.
Stock fork springs are 217mm long, or at least mine were, and the stock spacer length is 100mm (from end to end of the larger diameter). That's a total of 317mm. My new springs are about 273mm long, and I cut my stock spacer down to 39mm, for a total of 312mm. I did this mainly because with the stiffer springs it is more difficult to compress the spring when reassembling, but I'm pretty sure that after all is said and done, I hope to be very close. When cutting the spacer give yourself an extra mm or two for a margin of error. I gently used a pipe cutter to cut the spacer.
Place a piece of 300 grit wet/dry sandpaper on a flat surface and gently sand in a circular motion to get the end flat and smooth.
See, 39mm!
Fuzzy picture, but nice and flat and clean.
Notice the holes in the stock spacer. These are for the spring compressing tool that I don't have but I drilled some new ones anyway in case I ever get it. I tend to collect one-time-use tools at an amazing rate these days!
This is a good time to talk about fork oil level. Now, Honda recommends 90mm from the top of the fork tube, spring out, fork compressed. Many professional suspension tuners recommend the largest air gap possible to prevent bottoming on large bumps. The air gap acts as a separate spring as the forks compress. Depending on your riding style and weight you may want to make an adjustment. I will give you this much information: Too high of a level will cause the front wheel to skip off bumps. Too low of of an oil level and the fork will bottom out easier. If you want to make a change since you have the forks apart, now is the time but I'd recommend sticking with the stock level and ride it to see how the bike reacts. The thicker springs you are about to put in will take up more room, and thus will have some affect on oil level after everything's put back together, however Racetech makes no mention of oil level on their information page.
Okay, now it's time to put it all back together! Insert your new spring and put the joint collar in the spring collar. They may fit tightly together since you've cut the spacer. Slip the wire through the spacers. Take note of your wire around the damping rod and make sure it has a strong hold but is not bulky either. You will be pulling on the wire in the next few steps.
Slip the wire through the fork cap.
You will need to coil up the wire to fit under the socket like so:
Compress the spring with the fork cap and carefully thread the fork cap back into the fork tube. Be careful not to cross thread.
Slip the locknut over the wire. Now pull the wire so that the damping rod assembly comes up through the fork cap. You need to pull and turn the damping rod so that the 4 splines align with the 4 slots inside the fork cap. You will feel them mate and this will allow the damping rod assembly to come up even further as you are pulling on it. Carefully (without cross threading) thread the locknut onto the damping rod assembly. It may be a little difficult due to the wire being in the way. Adjust the wire position as necessary. BTW, both Traxxion and Racetech sell specialized tools for this but I'm a cheapskate
This is what it should look like when it's hand-tight.
Remove the lockwire. Now is when that ground down adjustable wrench comes in handy. You need to somehow fit the adjustable and the 12mm in there to snug the locknut down.
Install the o-ring, preload adjuster nut, and clip. Now do the other side.
Relax the bike onto the springs. Set sag. Now you're done!!!