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Henry Martin spends his nights writing fiction and poetry, which predominately deals with the often-overlooked aspects of humanity. He is the author of three novels: Escaping Barcelona, Finding Eivissa, and Eluding Reality; a short story collection, Coffee, Cigarettes, and Murderous Thoughts; and a poetry collection, The Silence Before Dawn. His most recent published project is a collection of Photostories in five volumes under the KSHM Project umbrella, for which he collaborated with Australian photographer Karl Strand, combining one of a kind images with short stories and vignettes. He is currently working on his next novel narrated in two opposing points of view. He lives with his family in the Northeast.

Sunday, February 16, 2014

WR250R fork service

During my last ride I had noticed some fork fluid leaking. While that was due to the icy conditions we encountered, and any water immediately freezing on the forks and the ice getting under the seals, I figured it was time to replace the seals and change the fluid anyway. At over 8k miles on the clock, it doesn't hurt to look at the internals.

The first thing that surprised me was how clean the fork fluid was. I had seen some forks (on other bikes) in the past, where the fluid was all dirty and cloudy. The WR oil was fairly clean, with no metal particles in it, and only slight discoloration.

So, this being my first time tackling USD forks, it took me longer than usual. On conventional forks, the procedure is much simpler, and takes only a few minutes. On the WR there are more parts to change, and the seals cannot be driven in with the inner/outer tubes apart.

These are the tools I used:
Nothing special. A Torque wrench, 17mm wrench (for a nut on the damper rod), 14mm hex (for damper rod base valve), a screwdriver (to pry the old dust seal, plus retainer ring), a small brass hammer, and an electric impact driver (air gun would have been better), and a little piece of aluminum barstock I had, where I notched it to keep the damper rod from spinning.

You will need seals of your choice and some fork oil. I went with Yamaha seals (the oem lasted fine) and Maxima 5W oil - 2 liters.

Loosen the fork caps on the bike. Once you remove the forks, remove the fork caps completely and turn the forks upside down. When all the oil drains, take out the springs and the little rod in the damper, move damper rod up and down a few times to drain rest of the oil, and set the forks on a bench.

With a screwdriver, carefully pry the dust seals out. Make sure not to scratch the forks! With the dust seals out, you can now see the retainer ring. Remove that as well. You can now hold the outer fork and carefully pull the inner fork tube out. It won't be easy, but it will work. This will also remove the oil seal. I ended up using the inner tube to drive the seal out, and it took only a few quick pulls.

Next, loosen the base valve - 14mm hex. First you have to remove the rubber plug in there (again, a screwdriver or a pick). The base valve is torqued and has Loctite. I used a wrench, then spun it fast with the impact driver. One of them came out fine, the other spun inside, hence the aluminum bar.
Once the base valve comes out, pull the damper rod, and set it aside.


Next I pulled the old bushings and seals off. (Yamaha calls the bushing "piston metal)

I wiped everything clean, then sprayed brake cleaner through all holes and on all internal surfaces. You do not want any sand or dirt in there. Here is a nice, clean fork.
Here is the old bushing vs the new bushing. Look at the wear on the inside (new one is on the left):
Next, with the forks clean, spread a little fork oil on the inner tube, and get a small plastic bag. I used the one that the parts came in. Slide the bag over the fork, lube it with some fork oil, and push your seals over it. This prevents damage to the seals during installation.
And here is how it all stacks up. Dust seal on top, bushing on the bottom.
Now, both my damper rods had a little bit of rust. I cleaned that off with 2000 grit sandpaper soaked in oil.
Now, grab your clean outer tube and your clean base valve, spread some oil on the o-rings and on the damper rod where it touches the inside of the fork tube,  and a bit of Loctite on the threads. Slide the damper rod all the way in, until it touches bottom. Hand thread the base valve into the damper rod, then use your impact driver (or air gun) to tighten it. If you go fast enough, it won't spin. Next, torque the base valve to  40ft/lbs (per manual).

With that done, slide your inner tube into the outer tube (lube the bushings and seals). The first bushing goes in easy, the second is a bit of a pain to seat. I used a small punch and a very gentle hand to get it started. Push it deep enough so you can start your oil seal. I don't have a seal driver, so again using a flat punch and a very gentle tapping all around, I seated my seal until I could see the retaining ring slot. Pop the ring back in, make sure it seats all the way, and compress your fork all the way.

Standing the fork vertically, fill it to the top of inner tube with your fork oil. You have to remove the spring guide and the rod inside the damper for this procedure)
 Move the damper rod in and out about ten times (slowly) and add fork oil as air is displaced. Then move your outer tube up and down (a little) about ten times, again adding oil to maintain oil level at the top.
When no more air escapes and the oil level does not drop, use your method of choice to extract enough oil to achieve oil level of 105mm from top (per manual). My method of choice is an old sprayer top with a straw cut to length. I just rest it on top of the fork tube and pump until no more comes out. It works great.
Next, put your clean spring back in, slide the damper rod up (took me a while to figure that one - I used a screwdriver between the coils to push against the nut on top). Once fully extended, put the collar back on the spring and thread your top cap by hand. Using the 17mm wrench, hold the lower nut, and using a 19mm socket torque the cap on at 11ft/lbs (per manual).

Bring the outer tube up, and temporarily crew in your cap bolt. Voila. You'll have to torque that after you have the forks back in the tripples.

What I do is to leave the dust seal on the fork leg without installing it. After I'm all done with all of the above, I compress the forks several times by hand, applying as much pressure as possible. Just push the fork leg against the floor (with a rag as a cushion) and lean against it. After I get tired of doing it, I look down at the oil seal to make sure that no oil leaked out. If satisfied, I press the dust seal in and call it a day.

Have fun!

Disclaimer. These are only my observations. Use your own judgement and your head. My writeup does not replace the use of factory service manual and all workplace safety measures. You cannot hold me responsible for doing something stupid. 








2 comments:

Unknown said...

Thanks for sharing! This is great. Performing my fork seal service soon!

leobb1003 said...

Thanks for sharing! you did me a great favor.