Replacing the Fork Oil Seals (Part 3)

Now that everything's apart, it's time for some cleaning. I bought one of these BBQ containers they sell at the supermarket for $2. It's big and relatively firm, and is not so light that it flies away easily.

I also got a paintbrush for cleaning for 80 cents. I tried to pick one with firm bristles.

I used paint thinner for solvent. It works very well for getting rid of dirt, oil and grease, but it really stinks. However, paint thinner doesn't leave any residue once it evaporates. If our local thinner is made from acetone, then it should also be a safe chemical to use, because acetone isn't harmful to health unlike things like gasoline (i.e. petrol). If it isn't, then there goes whatever's left of my brain cells.

You can also try kerosene or diesel, but please wear gloves. Some, if not most of these chemicals are carcinogenic (i.e. it causes cancer on prolonged contact).

I bought these nitrile gloves because I read that they work really well as a physical barrier against chemicals. These were a nice pair. I think they cost me around $5 a pair.

Cleaning the spring seat, spacer and bushing.

Cleaning the damper rod.

Being the tightwad that I am, I didn't want to waste a lot of thinner. So I saturated the brush with solvent, then dripped it into the interior of the damper rod to try to clean out the old oil.

The forks had some rust spots on them. So with the forks apart, I attempted to polish them up. My first attempt at using power tools for polishing.

I clamped the fork to the table and put some metal polish on it.

Then I attacked it with a teeny buffing "wheel" on the end of a drill.

Here's a close up shot.

Honestly it didn't work very well. I realize that I need to get proper polishing wheels and compounds, and this just isn't going to cut it. Another project for another day I guess.

I didn't take enough pictures for this project, so I don't have all the pictures for re-assembly. I'll take better pictures next time, promise.

But here's some other stuff I did before the forks went back on the bike. Here're all the parts cleaned up and laid out on the table. I lube the damper rod spring with fresh fork oil before re-assembly.

Then I lube the damper rod. I'm wary of that hole because of how much blood it's caused me.

I torque the screw according to the specifications in the manual.

I saw this torque adapter on sale on Amazon, and I thought it'd make a really neat tool. The reviews said that it was really accurate, so I actually bought it as a replacement for my torque wrench. Here's a closer view of it.

You can set the torque in various units, Kilogramme-meters, Newton-meters, Foot-pounds, or Inch-pounds. The torque readings only start to come on at 29 ft/lbs, so it isn't going to be able to measure anything below that. For working on a motorcycle, this just isn't going to cut it.

Moral of the story? Get a proper torque wrench.

After spending some time messing with it, I realized that it isn't very practical for several reasons. First, physical feedback is important in a torque wrench. This one beeps, and the LED changes colour when the torque setting is neared. That means you have to pull really slowly to hear that beep before exceeding the torque setting, and you need to be able to see the readout at all times. Besides, if you're working in a noisy area, things will go wrong.

Secondly, it's tricky to set the torque settings. The increments either move too slowly, or too quickly if you hold down the button.

Third, it's bulky and it doesn't ratchet. I cannot recommend getting this if you're thinking of using it as a replacement for a torque wrench. It might work as a calibration device, but not a tool for regular use. You'll also need a vice to use it as a calibration device for your torque wrenches.

To prevent damaging the inside lip of the new oil seals, I wrap a plastic bag over the top of the fork, and coat it liberally with fork oil. This is to enable the seals to slide over the top of the tubes without damaging the lip.

Next, you need to hammer in the fork oil seals. You're supposed to use a special tool for this, a fork seal driver. This is what the special tool looks like.

Before you do that, I highly recommend that you lube the inside of the fork lowers before you bang those seals in there. The fork oil is going to help the seals go in much easier. And they don't go in easy. On my first attempt, I spent close to 20 minutes hammering on the seal and didn't even get it to clear the retaining ring groove.

The picture below shows you where to apply the fork oil.

I didn't want to spend so much on a tool that I'm only going to be using very infrequently, so I made do with some PVC pipe. I got some 40mm PVC pipe and split it down the centre. Here's my improvised fork seal driving tool.

 Here I used my improvised seal driver to hammer in the fork oil seals.

 

Here's another shot of me driving my neighbours downstairs crazy.

Frankly, this plan didn't go very well. Problem was, the short PVC pipe was too light, and it just didn't give me enough leverage to drive the seals in properly. So I had another idea.

Introducing the "Big Kahuna."

It's a half a metre long 40mm PVC pipe. I suggest getting a larger size, perhaps 42mm. This one didn't fit the OD of the seals perfectly, although it did the job very well.

In fact, with this pipe, I took less than 15 seconds to bang the seals in so that they sit below the retaining clip's groove. Contrast that to the 20 mins I spent with the previous tool.

Here's another view:

I probably should clean up the edges with a file.

After I re-assembled everything, now it's time to fill it up with fresh fork oil. If I remember correctly, it calls for 472ml in each fork. I didn't want to dirty the only measuring flask I had in the house, which my wife uses for baking (I don't really fancy the taste of fork oil in cookies, do you?), so here's what I did.

I took a regular drinking water bottle, and cleaned and dried it. Then I measured 472ml of water with the measuring flask, and poured that into the bottle. Then I marked off the level of the water with a marker, and poured out the water, and let the bottle dry.

When it came time to refill the oil, I just poured the oil to the mark I made, and there should be 472ml in there. See? I didn't sleep during physics class.

It's important to get equal amounts of oil in both forks. I've read that unequal amounts will cause handling problems. Initially, I thought I'd just eyeball the oil level using a tape measure. I think the manual calls for the oil to be filled up to 137mm from the top of the fork.

At this point, I actually put everything back and fixed the forks back on the bike. But I kept having the nagging feeling that the levels were not level on both forks.

So I made tihs tool instead to help me accurately measure the level of oil in there. First you need a big syringe.

Then I get some clear tubing and fix it to the syringe. I taped a wooden chopstick on the end to make the tubing straight, so that it measures the level accurately. Then I mark off the required measurement (137mm) from the tip of the tubing.

With more time, I'll probably scrounge up some parts to make a better tool.

To use this, I just insert the tubing into the fork tube till the mark aligns with the top of the fork. Any excess oil can then be sucked out with the syringe, so the final level of oil in the fork is 137mm.

After that's done, the spring, spring seat and the spacer gets put back in.

 

The easiest way I've found to get the fork cap back on, is to push the fork cap down, and turn the fork tube (not the fork cap) anticlockwise, until you feel the threads engage. I found this much easier then trying to push down and screw in the fork cap at the same time.

Tighten it up, and that's one side done, and ready to go back onto the bike.

Well, that concludes our series on fork seal replacement. If you haven't already, please follow this blog.

If you have ideas or methods to do this better, please comment on the blog!

Thanks for reading, use your tools, and happy wrenching!