NC30 Race-Tech Gold Valve Installation
Although the NC30 is not (yet) listed in the Race-Tech suspension database, standard NC30 (L-N models, only; K-model NC30s use "damping rod" forks, and thus, may benefit from Race-Tech's "Cartridge Fork Emulators," but installation of that kit would be substantially different than for Gold Valves) forks can be re-valved with Race-Tech's FMGV S-2040 kitthe same one used on many other Hondas with 41mm Showa cartridge forks (CBR600F2-3, VFR750FL-V, CBR1000FP-T, etc.). NC30 forks are almost identical to late CBR600F2 forks ('94), except that NC30 forks are somewhat shorter and have different brake caliper mounts. Race-Tech straight-rate springs also fit perfectly, but they are so much longer than the stock springs that initial pre-load can often be set using a short stack of fork spring washers rather than a spacer cut from the aluminum tubing provided with the springs. For one possible way to set-up NC30 forks, see the NC30 Race-Tech Fork Specifications page.
Re-valving forks is not a difficult job, but it is a very unfamiliar one to most home mechanics, and does require the use of some specialized tools and techniques. The instructions below are not guaranteed to work for you, but they will, hopefully, make the process clearer. (The process could be made even more clear, of course, with the addition of digital photos of the whole process, but that will have to wait, unfortunately, until the next VSource.org Race-Tech Gold Valve installation...) For more information about the differences between cartridge and damping rod fork designs, an excellent primer is Race-Tech's article on cartridge forks.
The Gold Valve kit comes with a NTSC-format installation video that is, like certain of the other Race-Tech instructions, somewhat incomplete. In the video, Paul Thede, founder and owner of Race-Tech demonstrates or, rather, illustrates certain aspects of the installation of a Gold Valve kit on a set of Showa inverted forks leg from a Honda CR250 dirt bike. Plan on viewing the video a few times, both before and after you've disassembled your NC30 forks, if you've never been inside a set of forks before. Because the written instructions and the video both seem to have been written to cover dozens of models of forks, figuring out exactly how to apply the instructions to your NC30 forks may be a bit of a puzzle. Accordingly, it is a good idea to take your time and do a lot of test-fitting before reaching for the Loctite® and torque wrench...
In the Gold Valve instructions, Race-Tech lists certain tools that you don't really need, and neglects to mention certain others that you really do need. Forget the micrometerPaul Thede even says this in the video and tells you how to differentiate the thickness of the supplied shims without it (by bending them between your fingers: there are only two thicknesses of shims in the kit, and only a small number of the thicker shimsyou can easily feel the difference). One tool not mentioned is compressed air. This is absolutely necessary in order to clean the fork internals. The job is also very hard to do properly without a parts washing system of some kindeven if that is only kerosene (paraffin) in the bathtub...
Step 1: Stabilize the bike, using a rear or swing arm stand, and raise the front end so that the front tire is a few inches off of the ground. A small scissors jack placed under the engine (on the exhaust pipes) won't hurt anything. Remove the fender, axle, wheel, clip-ons, etc., but do not yet remove the forks or loosen the triple clamp bolts.
Step 2: Before removing the forks from the bike, loosen but do not remove the fork caps, because loosening them later would otherwise require you to clamp each fork tube in a vice to hold it from spinning, and doing this can scratch or distort the fork tubes. With the fork caps loosened, slide each fork leg out of the triple clamps.
Step 3: Clamp one of the fork legs in your bench vise and loosen but do not remove the Allen bolts at the bottom of each fork leg. Because it is a long reach to get to the Allen bolts, most Allen sockets will be too short. Professional motorbike mechanics generally have extremely long ones, but you can make your own from an un-needed Allen key. (These are very hard, though, so you'll have to grind off the end or use some sort of special hacksaw blade.) Before you start loosening the Allen bolt, make sure the Allen key is fully seated into the head of the bolt, because these bolts are known to be very difficult to remove, and stripping the head means a trip to a machine shop to get it drilled out. It is usually best to start with the impact wrench, because you'll probably need to resort to it anyway... (If the cartridge just spins inside the fork whe you try to loosen the Allen bolt, you can also try putting the fork under compression using a ratcheting tie-down strap, but if this gets away from you, somebody's going to get hurt...) (And if that doesn't work, try putting the fork under tensionsuggested by an experienced Honda mechanic.) Once you've loosened the Allen bolts, snug them back up so you don't drip fork oil all over the floor.
Step 4: Disassemble one fork at a time, and keep the parts (including the bushings, if you are not replacing them) from each one separate (this is necessary because the various parts wear-in together.) Follow the usual fork-disassembly procedure in the Haynes manual (i.e., do not take the pre-load adjuster off of the damping rod unless you are going to re-valve the rebound valve in addition to the compression valve) and dump out the old oil by inverting the fork over a suitable container. (The fork drain bolts can also be used, but this never gets all of the oil out, and often squirts it all over the floor.) Remove the Allen bolt and then the fork cartridge (note that it may still be full of oil). Separate the fork sliders from the fork tubes and inspect the Teflon®-coated bushings for irregular wear patternsif anything shows up, something's bent or pitted, so sort that out before you re-assemble the forks.
Step 5: To disassemble the fork cartridge, disregard the bit in the Race-Tech instructions about punch marks and drilling stuff out, just push the bottom of the cartridge up into the cartridge tube, and with a pick or very sharp screwdriver, remove the small wire c-clip from the bottom. Thread the Allen bolt back into the bottom of the cartridge temporarily and withdraw the compression valve body, followed by the damping rod (and the attached rebound valve) if you want to re-valve that as well. Disassembly of the rebound valve shim stack is a little bit more involved, and the video shows you the techniques you'll need to do this. (Note that there may not be enough shims in the kit to re-valve both the compression and rebound valvesyou will definitely have to use a micrometer if you plan on re-using any of the old shims because there is no other way to determine those shims' thickness.)
Step 6: Hold the compression valve body in a vise and loosen (but do not completely remove) the Allen bolt holding the shims and the valve onto the body. If your valve body is made out of aluminum (later model Showas have these, it may be that all NC30s use steel valve bodies...), slip a piece of heater hose, slit down the middle, around the valve body before clamping it in the vise to eliminate the possibility of scratching its machined surface. It is probably best not to take the shim stack off the Allen bolt until you are familiar with how you will build your new shim stack using the Gold Valve.
Step 7: Each Gold Valve needs to have one compression bleed hole carefully drilled into itno idea why Race-Tech hasn't done this already, but it isn't difficultprovided you have the correct size drill bit (#55, 1.3mm).
Step 8: The next step is to consult the Race-Tech Gold Valve Selection Chart included in the instructions and choose a shim stack. Your shim stack will probably be somewhere around c32, but this will largely depend on your particular riding weight, skill level and intended use. (You may note that the only difference in the stacks listed in the chart appears to be in the number of 0.15mmx17mm shims usedthe rest of the stack is nearly always the same.) When you are sure you have gotten the shim stack and Gold Valve properly installed, and know what to look for w/r/t binding between the spring and the cupped washer, put Loctite® blue on the Allen bolt and torque it to no more (and no less) than 30 inch pounds.
Step 9: Begin to put the forks back together by re-assembling the fork tube and slider with new (preferablethis will probably be the most convenient time to replace these) or the old bushings. The PVC pipe coupling works great as a fork seal/bushing driver on non-upside-down forks, because you can just slip it over the top and then whack it with a rubber mallet (it would work even better if you could find a length of PVC pipe that fit around the fork tube and extended above the top of the fork tube and you pounded directly on the end of the pipe). Once the bushings and seals are in place, you can insert the cartridge into the fork slider (don't forget the little cup that goes on the end), fit the Allen bolt, apply the Loctite blue, fit a new crush washer and torque the bolt to the proper torque.
Step 10: If you have Race-Tech straight-rate fork springs (FRSP S3534xx), you will next need to set the initial pre-load using aluminum tubing or spare fork spring washers (you will have at least eight on handfour from the spring kit and four from your forksthis should be enough). Follow the Race-Tech instructions, and ignore the part where they tell you to consult the "Type F" column in the chartsthat column didn't exist on the charts as of 1998. In any event, NC30 forks are "external top-out" forks, so follow those directions for determining initial pre-load. My springs were within 0.5mm in length of each other, but remember to measure each one, because they could differ more than that. When you are measuring the fork cap, make sure the adjuster is backed out all the way.
Step 11: Reassemble each fork leg, then bleed the cartridge and fill with the proper amount and weight of fork oil (measured from the top of the tube with the spring out, fork collapsed and the damping rod down as far as it will go). This should be 122mm from the top and 5wt fork oil. The hot tip for bleeding the cartridge is to thread the fork cap onto the pre-load adjuster until it covers the two bleed holesthis prevents oil from squirting out to the sides when you pump the damping rod up and down.
Step 12: Re-install your new, Race-Teched forks and go for a test ride!
|Copyright © VSource.org 1999-2005 [Sources: Race-Tech and Brian Whalen's old CBR900RR Web site]|