Changing Fork Seals

[Dirt Surfer]

Hey guys, I am looking for some assistance on changing the fork seals on my 01 cr250. I have the honda service manual but the instructions are not so good. It seems I have developed a leak on the right fork. It has never leaked in the past, but all of a sudden it is leaking a lot. I know I have to take the forks out, but do I have to completely disassemble the forks. Looks like I also have to take the large retaining nut off the top of the forks, not sure what it is called. If someone could provide some instructions I would greatly appreciate it.

Thanks,

jason

[Faded]

Jason,

I can walk you through it if you'd like. You pretty much have to take the forks completely apart to change the seals, it's not really hard but it is somewhat time consuming. Let me know exactly what you're unclear on and I'll try and help you out. It's to bad your post didn't come a week early, I could have taken pics for you. Let me know though and we'll get you through this. You're going to need at least 1 special tool (50mm fork cap wrench) and be able to make a fork seal driver (out of PVC) or you can buy the fork seal driver (the wi$er choice, but more $$$).

[Dirt Surfer]

Got everthing taken apart with no trouble at all. I am going to machine a seal driver tomorrow at work. It seems that the most difficult part of the job will be filling to the correct level. I bought the Honda SST?? 5W fork oil. I think that is what it is called. Hope this is good sruff. Any tips on filling would be great. Other then that, I just need to drive the seals in and reassemle what I took apart.

Jason

[Faded]

Not sure what you mean by problems with filling, just measure the amount (using a graduated cylinder or a Ratio-Rite works, has cc's on the side) and pour it in. Did you take apart the damper rod (unscrew the silver part out of the bronze/gold fork cap) to change the oil in there as well?

Be careful driving your seals in, you do not want to scratch the sliders (chromed tube). First I slide the dust wiper, the retaining ring, fork seal and the washer on the slider so it's ready to go. Place a sandwich baggie over the end of the slider so you don't inadvertantly tear the seal or wiper when putting them on. Then I heat the (gold) for leg with a propane torch so the seal will slide in easier. Now put the slider in the fork leg and line up the seal. I wrap the slider in a piece of shop towel and then put my seal driver around the slider. After that I push the slider down so that the (axle) end is resting on the top of the seal driver and use a rubber mallet to hit the axle mount to push down on the seal driver to drive in the seal. Hope it makes sense 'cause it works really smooth. There is even pressure on all sides pushing on the seal and it goes in really easy, especially if you heat the fork leg up a bit. Good luck, if you have any other questions let me know.

[Dirt Surfer]

I machined a seal driver today at work from aluminium. I will see if it works tonight. I did use the plastic bag trick to get the parts on the slider. Had not heard of the Propane trick. Yes I did take apart the innner and out chambers and cleaned real well. The old oil was pretty dirty. If all goes well tonight with the seal I should be up and running in no time. I only took one fork apart so far in case I needed the other for reference. I will keep you up to date.

Jason

[Faded]

Good deal, glad you decided to takle the job yourself and that everything is working out. You were smart to do one at a time, it's easy to forget the little things. Just curious, was it hard/expensive to machine your seal driver? I don't have a "real" one, I've just been using my ghetto PVC driver...if you're willing I would be interested in one.

[Dirt Surfer]

I machined it at work from aluminium, so it was free. It came out pretty good although I am no machinest. I am just an engineer with access to the nice equipment at work. Being that I made it from aluminium, I used your trick of wedging the driver between the seal and the axle holder and driving on the axle holder with a dead blow hammer. Driving the seal in with the aluminum driver was difficult by just sliding it up and down, so pounding on the axle holder worked great. The propane torch made it really easy. It is not a success yet as I have not ridden the bike to test it out. I could probably make you a driver in my spare time, it will be good lathe experience for me I do have a few questions about the manual and filling. Originally it said to add 180 (I think that is what it was) ml of oil to the inner chamber, then it said to set the oil column height 5-10mm above the step in the bore. For this I used the oil column height tool (worked great also). Why don't they just calculate the actual volume of oil to pour in and list that, as opposed to the two step process. Just curious. Then I had to pump the piston until the excess oil came in the spring chamber and then pour that out. All in all the job is easy if you have the RIGHT TOOLS (I had to make a few) , patience for the first fork (second is easy), and are somewhat mechanically inclined. Thanks for the tips.

jason

[KTM250rm393]

Jason,

if you ever get a slight leak in your fork seals. Slide the wiper down and get a piece of camera film and work the edge of the film into the seal and then slide the whole piece up in the seal area and work up and down all the way around the seal. One little piece of dirt or sand will make a seal leak like a stuck pig.

[Faded]

Originally posted by Dirt Surfer
I machined it at work from aluminium, so it was free. It came out pretty good although I am no machinest. I am just an engineer with access to the nice equipment at work. Being that I made it from aluminium, I used your trick of wedging the driver between the seal and the axle holder and driving on the axle holder with a dead blow hammer. Driving the seal in with the aluminum driver was difficult by just sliding it up and down, so pounding on the axle holder worked great. The propane torch made it really easy.

Good deal on the seal driver, that is awesome! I wish I had access to equipment like that. I too found it hard the first couple times trying to whack the seal driver, or (worse yet!) slide it up and down against the slider. Scratches on the slider will ruin it. I found it very easy and less susceptible to damage by applying heat with the torch and using the axle holder to put pressure on the seal driver. I'm glad it worked for you, that is what is important!

Originally posted by Dirt Surfer
It is not a success yet as I have not ridden the bike to test it out. I could probably make you a driver in my spare time, it will be good lathe experience for me

Let me know how it works out, you should be able to feel a slight difference, and maybe more if the fluid was really bad. If feels good just knowing it's changed. If you had the time and wanted to, I would really appreciate a seal driver! That would be awesome, way better than my ghetto PVC set-up! Let me know if/when you get around to it, and let me know what costs I'll incure (I know aluminum isn't free). Thank you!

Originally posted by Dirt Surfer
I do have a few questions about the manual and filling. Originally it said to add 180 (I think that is what it was) ml of oil to the inner chamber, then it said to set the oil column height 5-10mm above the step in the bore. For this I used the oil column height tool (worked great also). Why don't they just calculate the actual volume of oil to pour in and list that, as opposed to the two step process. Just curious. Then I had to pump the piston until the excess oil came in the spring chamber and then pour that out.

The only thing I can think of is that you can use the oil height in tuning the action, much like exploiting oil height/volume in the outter chamber. The excess oil you dump I would contribute to the displacement of the oil by the valve stack. Not much help here, I know how they go together, but I'm not a suspension guru too know how it's all suspose to work. I know just enough to be dangerous.

[KTM250rm393]

BTW,

If you want something lighter than a plastic bag. Sarin Wrap works awesome for protecting the seal when sliding it over the top of the fork tube.

[VET393]

Hey if anyone needs special drivers, I would be more than happy to make them for you. Give me dimensions and material you want them made from. PM me

[Florida 393]

To all,
There is a page on Garrett's site that tells how to make a low budget, highly effective seal driver. Check out the Motoman393 site for details.

Regards,
Bill

[VET393]

I have a question that pertains to this. the seal on the Yam was leaking and i fixed it by cleaning the seal out with a feeker gage.
How can I approximate the amount of oil to put back in the fork?

[Florida 393]

Vet,
If you know the fluid height with the spring removed and the fork completely down you just refill back to the correct level. If you did not have that information just measure the other fork's fluid level and fill to match. They should always be balanced in height and fluid viscisity. You will be good to go then.

Bill

[VET393]

TY Fla393