PROGRESSIVE FORK SPRING
INSTALLATION NOTES
4/19/01 - I had heard many great things about Progressive springs with regard to ride comfort and handling, and so I had to try them for myself. I was able to get the Progressive springs P/N 11-1128 for around $45.00. The following are my installation notes and some pics I took during the installation. If you are going to perform this modification make sure you follow your shop manual or Clymer's. This write up is really intended to display more or less what is involved with performing the modification. I haven't yet ridden with the new springs enough to comment on the difference other than say they are definitely stiffer. They stroke about 1/2 as far as the stock springs do when hitting the brakes. I will post an update once I have ridden more.
UPDATE 6/17/01: Well I have put about 1000 miles on the new springs now. I really do like them since they are not soft like the stock springs. Also, it has eliminated the problem I was having with my front pipes scraping in turns, as I did not scrape the pipe once while winding through the roads in North Georgia- only the pegs hit. Braking feels very solid now, and the bike doesn't dive nearly as much as it used to. This really helped and made the bike feel solid when preparing to enter the turns on the mountain runs. For such a low cost modification, I would recommend doing it if you are thinking about adding progressive fork springs.
This is a picture of the new springs. The springs are progressively wound meaning that the spring constant varies as a function of stroke. That is, the resistive force output from the spring is not linear as with a traditional wire wound spring. The progressive winding will allow the suspension to remain soft under low load conditions like cruising, but will tighten up quickly with stroke when the load is high, like when you apply the brakes.
With the bike on the centerstand, break loose the fork cap bolts using a 17mm allen wrench. Make sure you protect your bike from the wrench when it breaks loose.
Get the front wheel off the ground so you can remove it. This is so you can pump the fork to get the oil out if you are changing fork oil.
Remove the front fender and bracket.
Remove the speedo cable.
Remove the brake calipers and place something between the shoes to prevent squeezing the shoes together. It's too hard to get them apart if this happens.
Remove the front wheel.
Doing one fork at a time, remove the fork cap which is already loose from your first step. Push down as you loosen it, and put your hand over it so when it breaks free it won't fly off. The spring will uncompress, and the spacer will protrude out of the fork. There is a washer under the spacer. Remove the spacer and then slowly slide the fork outer tube up to get access to the washer and the spring, and remove them. If you are not changing the fork oil, you can just drop in the new spring and reverse the steps. Simple.
Here is a shot of the new spring next to the stock spring. The Progressive springs are about 19 7/8 inches long, while the stock springs are 20 1/8 inches long. You can also see the spacer and washer in this shot.
Next, I have a tool I made from an earlier fork seal project that can be used to hold the damper rod to prevent it from free spinning when removing the damper rod bolt. Have someone hold the tool, while you loosen the damper rod bolt to drain the oil.
IMPORTANT!!!!: With the damper rod bolt out, the
outer fork tube is completely free being held on the fork only by the fork seal
if you were to let it slide down that far. Also, there is an oil lock (taper
spindle) that fits between the damper rod and the bottom of the outer tube (see
sketch). Don't let the outer tube slide down far enough that the bottom of the
oil lock comes away from the outer tube. It might fall off the damper rod and
get cocked in the fork tube making it difficult to re-align. I can't remember from when I had my forks apart if the diameter of the oil lock is large enough to prevent misalignment inside the fork tube, but I'll be sure and check this if I ever have my forks apart again. If it were to get cocked, you might be looking at
taking the fork off the bike and separating the fork inner and outer tubes to fix it.
Here is how I did it. I had my wife hold the tool on top of the damper rod while I
loosened and removed the damper rod bolt. During this process, I pushed up on the
outer fork tube while she pushed down on the tool, thus keeping the oil lock
sandwiched between the bottom of the outer fork and the damper rod. Then I
shifted to where I could hold the tool and the outer fork. While keeping them
pushed together, I pumped the oil out by sliding the outer tube up and down with the
tool moving up and down with it. Once most of the oil was out (actually
practically all of it) I shifted back down to where I could put the bolt back in while my wife
again held the tool. Then, I just screwed the bolt back in about 5 turns or so just to limit
the stroke of the fork when I let go of it, but loose enough allow oil to
dribble out. I pumped the fork on occasion at this point, but by this time your only looking at a drip and a
dribble. Threading the bolt back in 5 turns
keeps the oil lock on axis so it can't turn sideways.
Since I had performed an oil change and fork seal change before, I knew exactly how much oil I had put in and I verified that the same amount came out. When you are finished draining oil, have your helper hold the tool again and torque the damper rod bolt. Drop your new spring into the fork tube followed by the washer and then the spacer. I positioned springs with the heavy end (tightly wound) at the bottom of the fork. My engineering background tells me that it makes absolutely no difference in the springs operation whether they are turned one way or the other, or even opposite each other, but I wanted the heavy end at the bottom. Low center of gravity is always better anyway. Plus, the spring will have less tendency to walk during the stroke (actually wouldn't make a difference in this application since the stroke is so short). Well, enough rambling, I put the heavy end at the bottom!! : )
Get a funnel, and pour in the new fork oil.
Once the oil is in, you can put the fork cap back on. This was probably the hardest part for me because you have to compress the spring and get the threads started. It takes a few tries but you can do it. Also, DO NOT drop the fork cap during this step. It is aluminum and has very fine threads that will dent if they hit anything. Also, be extra careful not to cross thread the cap. Take your time, push down and make sure it is aligned before threading it into the tube.
Once you have completed adding springs and oil to both fork tubes, put the wheel back on. Install the brake calipers and hook up the speedo cable. Remove your jack stand, and let the wheel come back to the ground with the bike on the centerstand. lower the bike off the centerstand and while straddling the bike, compress the forks a few times. Put the bike back on the centerstand, and put the fender and bracket back on.
Now, even though you kept the bike as clean as you could during all the steps, there will probably be some residual oil in the area of counterbore where the damper rod bolt head is. This oil will most likely blow out after your first test ride making you think its a leak. Wipe it off when you get back, and for several more rides continue stopping periodically to feel around the bolt to make sure there isn't a leak.
Have fun with your new springs!