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Installation Instructions for RPP Moto C4 Suspension Upgrade Kit

Installation Instructions for RPP Moto C4 Suspension Upgrade Kit

Please follow these instructions carefully. Ranger Point will not warranty damaged parts nor be held liable for equipment damage or personal injury resulting from improper installation or improper use of this kit. We strongly recommend professional installation.

  1. Remove front forks from motorcycle.

  1. Remove fork caps, then pull spacers, washers and springs from inside the fork tubes. Do this over a drain pan while pouring the oil out of the fork.

  1. After pumping and draining the fork, remove the damper assembly bolt from the bottom of the fork leg. A long reach 6mm allen wrench is necessary for this. We do not recommend the use of air impact tools on stubborn damper bolts. Better to hold the lower fork tube in a soft jaw vise and use a ratchet handle. Invert the fork and catch the factory damping rod as it slides out. 

No further disassembly of the forks is required.   

  1. Remove the teflon seals from their grooves in the factory damping rod caps and install them into the grooves on the RPP Moto damping rods. 

The C4 kit comes fully assembled and pre-tuned according to customer specs. It is not necessary to disassemble or adjust the units prior to installation. 

  1. However, should curiosity overcome, the new damping units can be inspected by unscrewing the red compression valve from the top of the damping rod using a 10mm wrench, then using the threaded extraction tool (provided) to pull the rebound valve out of the damping rod tube. Reassembly is the reverse. Be sure to fully seat the rebound valve and use only light bottoming torque when reinstalling the compression valve. Take care not to damage threads.

  1. Reinstall the damping rod bottom cups (if removed) into the fork tube, followed by the short, top out springs that go under the damping rod caps. Lower the C4 damping rods into the forks, taking care not to damage the teflon seals, then reinstall the damping rod bottom bolts, using the new crush washers provided. Be sure the old crush washers have been removed, and DO NOT USE IMPACT TOOLS to tighten the bolts.

  1. Test fit springs and spacers before filling the forks with oil. Lower the springs into the forks, then install any factory washers and spacers. With the forks fully extended, observe the height difference between the top of the spacer and top of the fork tube.

  1. Replacing factory fork springs. 

    1. When installing new, linear rate springs chosen according to rider weight, a good starting point for spring preload is 12mm (.5”). This is the total amount of spring compression when the fork cap is fully screwed on, and generally means the spacer will sit below the top of the fork tube. Measure fork cap height (under the shoulder stop) to determine how much compression will be caused. Do a little math, and trim spacers--or cut new ones--as necessary. New spacers can be made from simple PVC pipe available at hardware stores.

  1. When re-installing factory springs, which are often too soft, more than 12mm of preload is often necessary, particularly in the case of progressively wound springs. In some cases, the spacer will sit higher than the top of the fork tube. In all cases, final preload settings should be achieved with the owner/ rider sitting on the bike.  

  1. After setting preload, remove the spacer, washer, and spring, and begin filling the forks with oil.

Notes on oil: 

In damping rod forks, low speed compression rate is determined entirely by oil viscosity. In many cases the factory recommended oil (typically 10w in 41mm Showas) provides decent low speed compression damping, for offroading and comfort-biased street riding. Aggressive street riders may prefer a 15w oil. A very nice compromise can be reached by mixing the two viscosities closer to a 12w. The rebound low speed bleed in C4 kits is calibrated to match this range of oil weights. Thus, increasing oil viscosity will have an equal effect on both rebound and compression low speed damping, without compromising high speed damping adjustability. 

Because the RPP Moto suspension damping units are sealed, they need to be bled just like cartridge forks. The fastest way to do this is to extend the fork, place one palm firmly atop the open fork tube, then compress the fork and hold for several seconds. Air pressure will force oil into the damper. Repeat until the damper is “primed,” then stroke the fork until all air is expelled from the damper. Alternatively, the C4 compression valve can be removed prior to kit installation, and then installed after filling the fork with oil and bleeding the damper. The compression valve can be installed in the assembled fork using the included tuning tool. See separate instructions.

  1. Finish filling the fork to the recommended oil level, then reinstall the spring, spacer, and fork cap. Perform a manual bounce test on each assembled fork to ensure it is functioning properly.

  1. Reassemble the motorcycle. Perform a static bounce test on the assembled bike, holding the front brake and forcing the front end sharply downward, then letting it bounce back up. The front end should return quickly, but not overshoot by much, and settle to static height without any secondary bounce cycle. If all is well, complete the job by setting laden sag, typically ⅓ of overall travel.