AufRoad.com

My personal journey into adventure riding

New (proper) Fork Springs and Seals

CURRENT MILES

22,022

THE WHY:

When my 690 left the KTM Factory it was setup for a guy weighing 165 to 180 pounds. Obviously that guy is not me. I’m currently tipping the scale at 235 pounds (naked).

KTM also did not include in their factory setup was anything you might bolt on to the bike (crash bars, luggage racks, skid plates) and then what about all the actual luggage for a trip? I run a full Mosko Moto Reckless 80. The bike should be sprung for the actual weight it’s carrying, on the ride you want it best to perform on. For me that would be a fully loaded BDR style ride.

Back in April this year when I did the Bay Area Adventure Rally I had the chance to get a real weight of my bike, with my BDR camping and riding gear, and of course myself. We stopped at Tomm’s on the way out and put the bikes and then us on the scale(s).

Let’s say the bike weighs 350-ish stock. That would mean that 708 – 350 = 358 and that’s just about DOUBLE the weight that KTM allotted for in my current springs. DOUBLE!

Slavens has a great selection of the proper springs https://slavensracing.com/shop/fork-springs-ktm-690-hqv-701/. I gave them all my numbers and they suggested that I go with the .62 spring rate. If you do the math I fall right in the middle of that 254 – 276 slot.

So, I ordered the springs.

At the same time, while I’m in there… I ordered up SKF Fork dust and oil seals from Rocky Mountain. I didn’t have any oil leaks, but why go to all the trouble and not do it right?
Oh, on a whim I also picked up the Mud Scrapers – not sure if I wanted to go that way.

THE INSTALL:

Forks are really complicated but then again they are really easy if you just go step by step.

Just a side note. I’m not just doing the forks. I have a whole list of things to attack on the bike at the same time. Rear spring, fuel pump, safari tanks…

  1. I removed the front wheel.
  2. Since I am running a fuse block behind my headlight I needed to cut the 6 zip ties going around the fork tubes holding that in place.
  3. I unscrewed the caliper and speed sensor from the left fork leg
  4. I unscrewed the brake line holder on the left fork leg plastic guard.
  5. I unscrewed just the top triple clamp bolts. This holds the tubes in place.
  6. I then used an adjustable wrench to break the 24 mm top cap.
  7. Next, I loosened the bottom triple clamp bolts for each leg and slid them out.

With a clean area on the bench I started to disassemble the Compression (left) side first. These are 48 mm WP Open Chamber forks with 250 mm of travel.

  • Turning the knob clockwise, I counted the number of clicks to stop. It was 19.
  • Turning the knob counterclockwise I turned it all the way to stop. This releases the tension from the push rod.
  • Holding the fork upright, spin the top cap off from the top tube.
  • Next using your handy dandy thin 22 mm wrench, you can get in between springs or pull the springs down to hold the cartridge. It has to be thin and it has to be 22mm.
  • Now spin the top cap off of the cartridge.
  • I noticed that there were two plastic spacers in my top cap.
  • Next pull out the adjustment rod.
  • I put everything neatly in order on a clean surface as I went along. You can see the difference between the old spring and the new one.
  • Speaking of springs… since the springs run in a closed environment there’s a limit on the O.D. and so any additional steel has to be on the inside (I.D.). Slavens suggested that some springs might not fit over the spring guide.

Guess how my guides and springs fit? Yup, and they weren’t just tight, they were really tight!

The inside of the spring and the outside of the guides measured out to be roughly 32mm. I could force it, but that obviously was not right.

MODIFYING THE SPRING GUIDES

That meant that I needed to modify my guides to fit inside (with a small amount of free play). The first step was to remove the 7mm bolt at the bottom of the fork lower. Initially I didn’t need to do this unless I was going to mess with my shim stacks. Which I still may do in the future. I heard the best stack is one patterned off a 500 – but I still need to read more on that.

This allowed the cartridge to come out. Once out of the fork tube you can grab on to the cartridge shaft and they just thread off the shaft easily.

I figured the weapon of choice would be a table top belt sander running 120 grit. I set it up outside the garage and closed the door. Figured I wanted to keep as much of the dust out of the fork internals as I could.

Next, I simply sanded each of the 4 splines a bit, tested against the spring, rinse- lather – repeat, until I had adequate clearance.

I took a sharp razor and removed any of the flash around the edges, then a light hand sanding with a fine paper, and then a good cleaning with carb cleaner, rag and compressed air.

The springs now slide easily up and down the guides with no interference.

PUTTING IT ALL BACK TOGETHER

I kept everything I took off in a nice and neat order. I know this habit comes from my Father in the Porsche days. This is the compression side – but both look identical.

Start by making sure everything is clean. You wouldn’t want a small piece of crud to screw up the valving would you?

I noticed at the bottom of one of my cartridges that I had a circlip not fully in place. This is a good reason to visually inspect and clean everything before putting it back together. This was an easy fix. I pushed the shim stack up a little, got the circlip seat fully, then pulled the shim stack back down to sit against the circlip.

Speaking of circlips. On the disassembly I noticed the large circlip on one of the legs was really corroded. It’s just spring steel but they aren’t supposed to look like that. This one must have gotten wet and then stayed wet for some reason. BTW The other leg was not like this, just this side.

This was an easy enough fix as well. I just gave it a little rubbing with 600 grit wet/dry on a flat surface and we’re good to go.

BONUS CIRCLIP PRO TIP: You’ll need to pry these out of the fork uppers with a pick. There’s obviously two very different ends. See that upper end in this picture? The one with a little “S” cut off it? When the circlip is in it’s position in it’s groove you won’t be seeing it, but now that you know it’s there – that’s the side you are looking to get a pick under. It makes it so much easier! The flat angled side is obviously going to be harder to get under.

When I disassemble I also look for wear, bevels, markings, indentations. I noticed the metal spacer was beveled and made sure to note the orientation.

With everything clean I was ready to reassemble.

From left to right: thinner guide bushing, thicker guide bushing, beveled spacer, fork oil seal, retaining circlip, dust seal.

Note: I inspected my bushings and they didn’t show much sign of wear. You look at the Teflon coating.

Using a protective bullet, I slid each of the items onto the fork in the order, and direction they needed to be. The bullet protects the delicate edges as they slide over the sharp edges. Everything gets a nice coat of new fork oil as we go along.

Next, I put the two halves together making sure everything went in nice and straight.

The fork oil seal is the first thing to address. I have the Tusk 48mm seal driver tool. You can count the number of cartridge forks I’ve done on a Woodshop teacher’s right hand and I’m honestly surprised every time just how much effort it takes to drive the seal home. When the seal is fully in you will know it because you can see the retaining circlip groove.

In this picture you can see that I held the unit upright against the workbench using two hand clamps. Simple and easy to manage.

Next comes that retaining circlip I had polished up. I made sure the clip was fully in and easily rotated in it’s groove.

The dust seal is next and it did not need to be driven in. It was more a just an easy push to get fully into place. I decided NOT to put in the mud wipers I had bought – at least for now. If I did put them on the black rubber collars would need to come off. It’s pretty easy to do as they just sit in that groove.

Next it’s time to fill with oil. I’m using Belray 5W Fork oil.

The manual calls for 635ml per leg as a capacity but then we’re going to set the final volume up by measuring the distance from the top so this is just a starting point.

I made a small little mark on my funnel on where 635ml should be. It’s not precise but then again it doesn’t have to be. We actually want more than the capacity to start.

Next I put the adjustment rod down the middle of the cartridge, bottomed everything out and filled the fork tube. I slowly moved the cartridge up and down multiple times, making sure all the air was out of the system. I gave it a few minutes for any trapped bubbles to rise as well.

To measure the distance from the top of the fork tube I have special tool. It’s a syringe with a hose that goes to a rigid tube. There’s a collar that clamps on the tube that then sets the maximum fill level.

Here’s a closer look.

There are markings on the tube but I used my calipers just to make sure the distance from the collar to the end of the tube was exactly 125mm.

Now, with the fork vertical, you drop the tube into the fork until it’s resting on the collar. Pull back on the syringe and suck up fork oil until it starts sucking air. Now you know it’s at 125mm! Simple!

Next I pulled up on the cartridge until it stopped. I dropped the spring down in the hole making sure it was seated at the bottom where it was supposed to be (by feel).

My fork springs are way taller than the top of the cartridge so somewhere in the middle I snuck my thin 22mm wrench and grabbed the hex of the fork guide. I would have taken pictures of this section but I needed both hands and could have even used a third or forth.

By rotating the spring I “screwed the spring down on my thin wrench until the shaft was sticking out the top of spring. I could then manage to get most of the top cap threaded on. I would guess I was threaded 60% of the way. With a quick pull I pulled the thin wrench out from between the spring, made sure the spring was centered in the cap. This required just a little finagling to make sure it was 100% correct. I then repositioned my thin wrench and finished tightening the top cap to the cartridge with a 24mm on top.

Next I slid the outer fork tube up and screwed it onto the top cap. It just needs to hand tight right now. We’re going to put it in the bike and then worry about torque. With that, I was basically done.

NOTES:

On the Rebound side I was draining the oil and the fork was hanging upside down. I didn’t see it at the time but I had two small parts plop into the oil pan.

I kind of knew what they were. This is the “jet” that sits at the end of your adjustment rod and controls how much oil is shot up into your shim stack on impact. You would never see it but inside the fork it should look like this. I am questioning if this is stock. It’s kind of weird that it’s red anodized – to me that says aftermarket. I did not pull out my shims stacks to check.

I made sure when I put the rebound side together that I got that into the right spot as I was building it all. It’s all by feel as there’s now way to see any of this. I’m not sure why the compression side didn’t fall out too. I know it’s in there because you can give the rod a press and feel the little spring do it’s thing.

Torque Specs:

  • 7mm Allen bolt at bottom of Forks: 25 Nm / 18.4 Ft Lbs
  • Top Cap of Fork Legs to Cartridge: 25 Nm / 18.4 Ft Lbs
  • Top Cap of Fork Legs to Fork Tube: 40 Nm / 29.5 Ft Lbs
  • Upper Triple Clamp Bolts: 17 Nm / 12.5 Ft Lbs
  • Lower Triple Clamp Bolts: 12 Nm / 8.9 Ft Lbs
  • Brake Caliper Bolts: 25 Nm / 18.4 Ft Lbs
  • Axle Pinch Bolts: 15 Nm / 11.1 Ft Lbs

Set both to 10 clicks? That’s what the manual suggests. We’ll see. I’ll start at 20 and move that direction.

TRUE CONFESSIONS:

It really didn’t go exactly like that.

I put together the entire Rebound side, looked up and said to myself,
“Why is that new spring sitting on the workbench?“.

I had put it all back together with the old spring. DOH!

Mike Mueller
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