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Upgrading the Front Suspension |
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| Written by Pat Martin (USAFRETIRED) | ||||||||||||||
| Thursday, 10 March 2005 | ||||||||||||||
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Front Suspension Maintenance and Upgrades I made some changes to my bike this winter and decided to upgrade the front suspension. There are several things you can do such as change the type of fluid, weight of fluid, upgrade the springs, or add a set of Gold emulators. I decided to do all four, so lets take a look at some of the steps required to do this.
Tools and Supplies used:
Keep in mind that some steps I did may not be required for what you are planning to do. This article describes the steps I took to completely change over my front components to chrome items, change the fork springs, change to a synthetic 10 wt suspension fluid, and add Gold Emulators. Preliminary steps needed:
1. The pinch bolts in the top tree are putting pressure right around the area where the fork tube caps screw in. You need to loosen the pinch bolts on the sides of the top tree first. Only after the top pinch bolts are loose, then break loose the fork tube fill caps. Do not remove the caps as they have a spring under them and we will discuss their removal later. Remove the top stem nut in the middle of the tree and lift the top tree off. You can now remove the top fork tin covers. Make sure that you do not loose the rubber grommet and metal washer inside the tins. When these items are removed, it will look like the first picture in this article. 2. While holding a fork leg to prevent it from sliding downward, loosen the pinch bolts on the side of the lower tree. Once these bolts are loose, the fork leg will slide downward and can be removed from the bike. Repeat for other fork leg.
3. With the fork legs removed from the bike, we can begin disassembly of the front forks. Find yourself a workbench and have some rags handy as we are going to get into some oil. I had to make a hex key that was long enough to go up into the bottom of the fork. I took a 6 mm hex key and cut it off, then used a 6 mm socket on the hex key. I could of used a long hex key but I needed a tool to torque the bolts back in later anyways. Break loose the dampner bolt found in the bottom of each fork tube but do not remove it. Be advised that oil can leak from this bolt, so do not loosen it to much.
4. Now that our dampner bolt is loose, we can stand the fork assembly on end to loosen the top spring cap. Be careful, this cap is under pressure from the spring. The cap plug has fine threads, once it reaches the end of those threads, be prepared for the spring to push that cap up quickly. Holding your hand over the cap, take the cap off until it is removed. The picture below shows how far the spring will push the cap up.
5. Here is where you will find those rags handy. Remove the spring from the fork tube and set it aside. With the spring out of the way, lets get rid of the majority of that oil. Using that oil pan that you had ready, turn the fork leg upside down to drain the oil.
6. We need to go back now and finish removing the lower dampner bolt. If the bolt does not remove, the damper rod is spinning with it. If this happens, then there are two ways to remove the bolt. You can use a dowel rod or broom handle to stick into the fork tube to apply pressure to the top of the damper, or use an air ratchet to spin it out. Once the dampner bolt is out, the damper and the small spring will slide out of the top of the fork. Turn the fork tube upside down to remove the damper rod. 7. It is time to take those fork legs apart. First thing we want to do is remove the upper seal. Take something like a flat screwdriver or putty knife and work the edges up. Be careful that you do not mar the surface of the lower leg up while attempting the remove the seal.
8. Underneath that top seal you will find a spring clip that sits inside a groove. With a small screwdriver, work the end of the clip out of the groove and remove the clip. Do not attempt to remove the rubber seal that is below the metal clip, we will get to that in the next step.
9. The next step will separate the fork tube from the lower leg. With the fork assembly over some rags on a workbench, grasp the lower fork leg in one hand and the fork tube in the other. Collapse the fork assembly together softly. Be careful not to bottom out the assembly with force as you can cause damage to the internal parts of the fork. With the fork assembly collapsed, pull apart the two assemblies forcefully. We are using the lower slide inside to contact the upper slide. This will force the upper slide out of its seat and allow to two pieces to separate into two assemblies. It might take a few attempts to separate them. After they separate, you can inspect and reuse the seals and slides, but I recommend replacing them. The cost was not that much and I figured I did not want to tear these back apart because of a bad seal that I missed.
10. My plans were to change the springs over to a set of Progressive springs. So you are wondering what the difference is between the Stock springs and Progressive springs? Stock are straight rate springs meaning that if you have a 20lb. straight rate spring it will take 20lbs. of force to compress the spring one inch. Then it will take 20 more lbs. of force to compress it the next inch, and so on, until the end of the travel. A Progressive Rate Spring has the advantage of a rising rate resistance to compression. For example, a 15lb. to 25lb. Progressive Rate Spring will take 15lbs. to compress it the first inch, then 17lbs. the next inch, and so on, until the end of the travel; it will take 25lbs. to compress it the last inch. The benefit of this is that the spring can be soft enough at the start of the travel to offer a softer ride yet be stiff enough at the end of the travel to soak up the big bumps. It will also reduce what is known as front-end dive under braking. As seen in the picture, the progressive spring have more spring wound closer together at one end and they are also shorter than the stock springs.
11. Since the Progressive springs are shorter, the instructions will tell you to make a 6 ˝” spacer and use flat washers at both ends of the spacers. I used PVC pipe to make the spacers. But since the springs sit on the emulators that I planned to install, I reduced the PVC spacer the thickness of the emulator which was ˝”.
12. The next step was to make the modifications required for the Race Tech Gold Emulators. The emulators that I installed are listed by Race tech as fitting the Yamaha Royal star. Race Tech does not list them for the Roadstar. The internal size of the lower leg is the same so they will work in the Roadstar as well. I contacted Race tech about not being listed for the Roadstar and asked if they might look into the matter. I had also contacted Daniel Rand, the Service Manager at A-1 Sports Center for his advice, as I knew he had installed many sets of the emulators. Dan was a great help and has always given his advice freely if asked. 13. So about now you are probably wondering what these emulators are? They are basically an adjustable valve system that takes over for the function of the damper rod. The damper rod has a hole in the end of it and this partially controls the fluid movement with the fork tube to the lower leg. One size hole only allows so much fluid through at a time. The emulator system disables the damper rod hole and sit on top the damper rod under the fork springs. They allow the amount of dampening action (fluid travel) to be adjustable to suit the rider. Daniel Rand recommended 6 to 7 turns of preset on the emulator and I set mine to six turns. Follow the instructions included with the Emulators to adjust them.
14. The steps to install the emulators require that you drill out the hole in the damper rod and also add two more additional holes. This serves two purposes; it disables the damper rod and also lets enough fluid to get to the Gold Emulator because it is taking over control of fluid travel. I drilled the holes per the instructions included and noted that the lower hole I drilled was actually going to be inside the cup that the damper rod sits in. I contacted Race Tech about this and they advised that I could drill the holes above the existing one. But as seen in the pictures, I had already drilled the holes prior to the call and the holes were drilled. Dan at A-1 said he had drilled his like mine and had never seen a problem with it, so I stayed with the holes I had. Ensure that all the burs and rough edges of the holes are removed.
15. Now that the damper rod has been modified, we are ready to reassemble the forks. First thing I need to stress is keeping everything clean. You do not want any dirt or lint inside these forks. (Note: If you had you fork legs chromed, ensure that there is no chrome residue in the location where the upper slide seats. If there is, it must be cleaned out or the fork tube will jam upon installation of the upper slide.) Did I mention how clean you want to keep everything upon reassembly? I cannot stress it enough. I chose a synthetic Ten-weight fluid for the forks.
16. Replace the lower slide with a new one and coat it with the suspension fluid.
17. Coat the seal at the top of the damper rod with suspension fluid and install the small spring onto it. Then slide it down into the fork tube. Reinstall the cap on the end of the damper rod.
18. Lubricate the upper slide with suspension fluid and install it over the top of the tube. Then install the flat washer over the top of the slide. (Note: The upper slide shown in the picture will install at the top of the fork leg and will require a special tool to install.)
19. You now want to coat the walls on the lower fork leg with suspension fluid. Guide the fork tube inside the fork leg with the lower slide going down into the fork leg until the oil flow stopper cup bottoms out in the bottom of the fork leg. The upper slide and washer will stop at the top of the fork and the washer will assist with keeping the fork tube center in the lower leg. You want to now reinstall the dampner bolt at the bottom of the fork leg. More than likely, the damper rod will turn while attempting to reinstall this bolt. If it does, use a large dowel rod to go down inside the fork leg to hold the damper from spinning. Ensure the crush washer is on the bolt and you have put some Loctite on the threads. I used blue (removable) Loctite. I would not recommend using a permanent Loctite such as most of the reds. You can torque this bolt now or later in the procedure, but do not forget to torque it. 20. At this point, you will need a fork seal driver 43 mm in size to drive the upper slide down into its seat.
21. Using the driver against the flat washer you installed, you will drive the upper slide down into its position in the top of the fork leg. It will take a few hits to seat it. (Between the drives on installing the upper slide, ensure the fork tube remains free by attempting to rotate it. If you cannot rotate the fork tube, you will need to stop and disassemble to find out why the slide is binding the fork tube. The tolerance is tight so any chrome or foreign object will cause binding.) Once the upper slide is installed, you can lubricate the lower seal and install it using the seal driver. The picture below only shows the order reference for the washer and seal. Drive the upper slide and lower seal separately.
22. Reinstall the spring clip ensuring that the clip is fully seated into the grooves of the lower leg. Then install the new upper seal.
23. Install the Gold Emulators. They will lower into the fork legs and rest on top of the damper rod. At this point you are ready to fill the fork legs with suspension fluid. Always follow the instructions that come with the springs that you decide to use. With the fork springs still removed, collapse the fork assembly. If you are using stock springs, follow the service manual for the oil level to be set at 110 mm. If you are using the progressive springs, then fill the forks until they are 140 mm or 5.5 inches from the top of the fork tube. The reason this measurement differs is that the progressive springs displace more oil than the stock springs. Cycle the forks up and down about a dozen times to distribute the oil and recheck the fluid level with the forks collapses again. Add fluid as required until the measurement from the top of the fork tube to the fluid is achieved. I used a digital caliper to measure, but anything that will measure for you will work. 24. Once you have the fluid at the desire level extend the fork legs. Install the spring down the tube (close wound end facing downward) and on top of the emulator. Now install a washer on top of the spring, the spacer you made, another washer, and the cap. Part of the spacer and cap will be sticking out of the tube. The cap is a fine thread and is a little difficult to reinstall. The easiest way I have found to reinstall the cap is to put a large rag on the floor and rest the assembly on the rag. Get a helper to hold the assembly for you and keep the tube extended. You push the cap and spring down with the palm of your hand until it feels like it is sitting flush on the threads. Have the assistant turn the tube counterclockwise and this will ensure the threads are flush. Once you feel the threads are flush, have the helper turn the tube clockwise until the threads start. Do not force this cap on, as it will strip easily. You can now torque the lower dampner bolts in the fork legs. 25. You are now ready to reassemble. Install the top tree and tighten the center nut snug. Slip the fork tube into the bottom tree and raise it to a point just slightly above the top tree. Lightly pinch the bolts in the lower tree enough to hold the fork tube. Install the other fork tube in the same manner. Once both fork tubes are set, remove the top tree and reinstall the top tins. Reinstall the top tree and retighten. The reason I had you leave the tubes slightly above the top tree is because the top tins have those washers and rubber grommets in them. They will make the top tree set slightly higher than it was without the tins on. Check to make sure the fork tubes are level with the top tree. If any adjustment is required, you will need to disassemble and adjust the fork leg within the tree.
26. Once the fork tubes are at the proper height, you will need to go back and torque the pinch bolts on the lower tree. Torque the fork tube caps (Do this before tightening the top tree pinch bolts). Then tighten the top pinch bolts in the upper tree.
The remainder is reassembling the bike per the manual and torque all fasteners. Questions should be asked in our forum (Use discuss link below). The forum is very active and you stand a good chance of getting your questions answered there. If you would like to leave feedback for the author, or have additional information you think will benefit others, please use the comment section at the bottom of this page. Discuss this article on the forums. (1 posts) DISCLAIMER: This information and procedure is provided as a courtesy and is for informational purposes only. Neither the publishers nor the authors accept any responsibility for the accuracy, applicability, or suitability of this procedure. You assume all risks associated with the use of this information. NEITHER THE PUBLISHERs NOR THE AUTHORs SHALL IN ANY EVENT BE LIABLE FOR ANY DIRECT, INDIRECT, PUNITIVE, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, OF ANY NATURE ARISING OUT OF OR IN ANY WAY CONNECTED WITH THE USE OR MISUSE OF THIS INFORMATION OR LACK OF INFORMATION. Any type of modification or service work on your motorcycle should always be performed by a professional mechanic. If performed incorrectly, this procedure may endanger the safety of you and others on your motorcycle and possibly invalidate your manufacturer’s warranty.  Quote this article on your site | Views: 47886
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