Installation: Touratech Fork Cartridge Conversion for BMW F750/850GS

Converting your F850GS’s front end with a high-performance, closed cartridge fork kit from Touratech Suspension will wake up the front of your BMW and make a huge change in handling, stability, and performance in any of the on and off road conditions you find yourself riding.

Not just a change in spring rate, or a simple re-valve, this cartridge conversion completely transforms the front-end of your F850GS with all new damping characteristics that can’t be achieved with the stock F850GS or GSA¬†forks.

The F850GS and GSA use a single fork leg to control both the compression and rebound damping, this reduces the weight of the forks to improve steering responsiveness both on and off pavement. The Touratech single sided cartridge kit replaces the stock internals with much more capable components to drastically improve the wheel control without adding unnecessary weight to the fork. Additional benefits of this design are a significant reduction in installation time and complexity as only a single fork leg needs to be removed from the motorcycle.

Gone are the days of non-adjustable stock front suspension. The Touratech kit is completely tunable with rebound, compression, and preload adjustments made from the top of the fork caps. No matter where your adventure takes you, you can be assured that our cartridge system is designed to go the distance and tackle any terrain you throw at it.

VIDEO TRANSCRIPT:

Hello, I’m Ian with Touratech-USA and this is going to be your installation video for the Touratech Fork cartridge conversion that fits the BMW F850GS and F850GS Adventure. The installation is very similar between the two bikes. The only real difference is the oil height measurement, but we’ll cover that later in the installation. A lot of people don’t realize that all of the damping on the front forks of this bike is controlled in just the right side fork leg. And that makes the cartridge conversion installation a heck of a lot easier on this bike because you only have to disassemble one fork leg.

So I’m going to break this down, we’re going to go through the installation and you’re going to see just how easy it is to drastically improve the fork performance on these motorcycles. A lot of guys complain about brake dive and suspension bottoming with the stock setup. And this is a huge, huge upgrade that really addresses both of those issues.

So the first step is to jack up the bike so that the front wheel’s off the ground and then we’re going to remove the front. To remove the front wheel on this bike, loosen the two pinch bolts on the clutch lever side fork leg. Those use a Torx T-40 driver. Then loosen the axle nut, that uses a 12-millimeter Allen driver. Then you can loosen the other two pinch bolts on the throttle tube side fork leg. Then you just slide the axle out to the throttle side and drop the wheel out.

Now that we have the front wheel removed from the bike, it’s time to unbolt everything that’s connected to the throttle side fork leg. That’s going to be the lower fender, the brake caliper and the brake line bolts. The low fender is held onto the fork tube with three Torx T-30 bolts. The brake line junction block is bolted to the fork leg with a single Torx T-30 bolt. The brake caliper is held on with two Torx T-50 bolts.

All right, now that we have the wheel off and we have all of the things that were bolted to the fork leg unbolted. Before we remove the fork leg from the bike, we’re going to break loose the bolt that holds the stock cartridge in at the bottom of the fork leg. And after we loosen the top clamp, we’re going to loosen the fork cap a couple of turns. We are not going to completely remove either of those two things. We just want to break them loose while everything’s clamped on the motorcycle here.

The cartridge retaining bolt on the bottoms side of the fork leg uses a six-millimeter Allen wrench. The upper fork clamp uses a Torx T-40 bolt to tighten it up. Once we’ve loosened that you can use a large crescent wrench or a 31-millimeter socket to loosen the fork cap. Now that we have the bolt at the bottom of the fork leg broken loose and we’ve also broken loose the fork cap at the top of the fork, it’s time to loosen the lower fork clamp using two Torx T-40 bolts and then slide the fork down out of the clamps.

When both of the fork clamps are loose, just a gentle twisting and downward pressure will bring the forks slowly out of the clamps. All right, we’ve got the fork leg out of the bike. Now’s a great time to clean off any dirt from this fork leg to make sure we keep it nice and clean while we’re working on the insides. Okay, so I’ve got the fork leg out of the bike. Everything’s nice and clean ready to work on. I’ve grabbed an oil pan right here and I’ve loosened the fork cap enough when it was on the bike that I should be able to just spin this off by hand. And I’m going to turn the fork upside down and start draining the oil into the pan.

Okay, you saw in the video there that when I tipped the fork upside down, all of the cartridge and all the guts and everything came right out of it. Now, I didn’t expect that to happen because that’s not normally how these things come apart. I did a little bit of digging into it here while I was cleaning everything up and I found out what happened. So this is the bolt that goes in the bottom of the fork tube right here. And there was some sealant on it from the factory that had kind of glued the bolt head in place in the bottom of the fork.

And so when I loosened the fork cap at the top, it actually spun the entire cartridge assembly around this bolt. And then when I tipped it upside down, everything came apart. The spring came off, the spacer and everything. So yours probably won’t come apart like that, but if it does just make sure there aren’t any pieces left inside the fork. Make sure the bolt comes out and the threads are clean on it and you’re good to keep going forward with the installation.

Normally, what would happen is you’d have to remove the fork cap from the top of the damping cartridge like this. That’s done by putting the crescent wrench on the top here and a small spanner on this locknut underneath, and just turning them loose and then taking the fork cap off. At that point, then you can take the spring and the spacer all out. Then you would loosen this bolt on the bottom of the fork and slide it out of the fork leg. Mine just decided to come apart quickly and give me a shortcut that ended up taking me a longer time because it scared me.

So at this point, we’re good to continue on with the installation, however. So you’re going to need the bolt that comes out the bottom of the fork leg and the copper washer on it. You’re going to reuse all of this, so set that aside. The fork leg itself, of course we’re going to reuse, but all of the stuff from the cartridge, the spring, the stock cartridge, the spacers, the fork cap, everything else, you can just set that aside. I recommend laying out a piece of cardboard and just putting on there because it’s going to be oily and dirty and gross.

Make sure you leave your fork leg inverted for a few minutes to let all the extra oil and everything drain out. And if the oil’s especially dirty, maybe give it a good spray out with some brake cleaner to make sure you get all the particulate out of there. It’s not critical because our system is a closed cartridge. So all the damping oil is contained inside the cartridge, but it’ll just keep the oil in the fork that’s lubricating the slider bushings clean a lot longer if there’s not a bunch of garbage in there right from the get go.

Now we have to remove the fork cap from the Touratech cartridge. In order to do that, you’re going to need a 15-millimeter slim wrench. That’s five or six millimeters thick at the head and a 22-millimeter wrench to grab the preload adjuster knob on the top. If you only have SAE wrenches, that’s a 5/8s and a 7/8s. So first thing I like to do is slide the 15-millimeter wrench into the locknut at the top of the fork cartridge. To do that, you have to push down on the ring to expose the nut and then slide the wrench in.

Once you have the wrench in, take your 22-millimeter and put it at the top on the preload adjuster knob and then loosen the preload adjuster knob on the top. Once you’ve broken it loose, you can just spin it off by hand. I also like to remove the damping adjuster rod just keeping it out of the way. Put it somewhere safe so it doesn’t get dropped or damaged, that way it won’t fall out if you turn anything upside down.

Now you can push down on the spring and remove your 15-millimeter wrench. Grab the two spacers and the spring itself, and slide it off the top of the cartridge. At this point, another good practice is to turn the locknut clockwise all the way until it bottoms out on the threads. That way you know it’s always in the right position where it needs to start when you’re reinstalling the fork cap. Now that we’ve removed the fork cap from the Touratech cartridge, done on all the disassembly with the different pieces and screwed this nut all the way down, it’s time to put the fork cartridge into the factory fork leg. And then fasten it from the bottom using the original bolt and copper crush washer.

I torqued this bolt at the bottom up to about 15 foot lbs. Now that the fork cartridge is installed in the fork leg and we’ve tightened up that bolt at the bottom, grab the 15 weight fork oil that comes with the cartridge conversion. And you’re going to fill this fork all the way up until it covers the holes in the top of the slider here. And then we’re just going to work the fork up and down a whole bunch of times like this to bleed out any air bubbles.

It’s important not to extend the fork further than about the stock travel because if you bring it really far up, you’ll expose the sharp holes up at the top of the lower slider and you could damage the fork seals. Once the fork leg moves through its full travel very smoothly and you’d don’t see any more bubbles coming up in the fluid, that means that you’ve got the fork bled properly. Now we’re going to grab a syringe and a piece of hose, and we’re going to set the air gap at the top of the fork.

Now that the fork has been filled with oil and we’ve bled out all the air bubbles, it’s time to set the air gap at the top of the fork. The easiest way to do at is to use a syringe and a piece of hose, and draw a line at the hose where you want the air gap to be set. The F850GS and GS Adventure actually use the same range. We recommend a 65-millimeter air gap for all around riding and a 60-millimeter air gap for more off-road-specific riding.

So the way to do that is you actually compress the fork cartridge all the way down into the fork so it’s displacing all of the oil that it will be displacing. And then you line up your mark at the top of the fork leg and then suck out the oil until it comes to the height that you’ve drawn your mark at. This is something that’s a lot easier with a second set of hands, but we’ll see how we get along here.

The air gap is now set properly in this fork so it’s time to reassemble the spring, the damping adjuster rod and the fork cap and then we’re going to close up the fork.

Don’t forget to reinstall the damping adjuster rod before you put the fork cap on. Before you install the fork cap, make sure that the locknut on the cartridge rod is screwed all the way down until it bottom out. Then you can screw the fork cap down all the way until it stops. And then you’ll tighten up the cartridge rod locknut until it hits the bottom of the fork cap. Once you’ve tightened the locknut between the fork cap and the cartridge rod, you can slide up the black portion of the fork body and screw the fork cap down into it.

You won’t be able to get the fork cap all the way tight until we have it back into the clamps on the motorcycle. Now is the time to reset the damping adjuster. Turn it clockwise gently until it hits the stop and then turn it out 10 clicks to get back to the factory default setting. The cartridge kit is now installed in this fork leg, so it’s time to reassemble the forks at the front of the motorcycle. Twist the fork leg while applying gentle upward pressure to slide it up through the clamps.

Once you have the forks slid up into the triple clamps to the appropriate height, tighten one of the lower fork clamp bolts to hold the fork in place. While we tighten down the fork cap. Use the provided pin wrench from the cartridge kit to tighten the fork cap. It doesn’t need to be really tight, just enough to make sure that the fork cap stops spinning and is locked down against the top of the fork tube. Once the fork cap is tightened, loosen that lower triple clamp bolt and then rotate the fork to make sure that the writing on the fork cap is facing the correct direction, and confirm that the fork height hasn’t changed while you were doing this process.

Now that I’m done adjusting the height and the orientation of the fork here, it’s time to tighten down all of the fork triple clamp bolts. The Torx spec on these guys is 19 Newton meters. That’s about 14 foot lbs and there’s two bolts on the bottom so you have to make sure that you tighten them alternating so they both come down to the final torque, and there’s a single bolt on the top clamp.

The fork is now installed and the upper and lower triple clamps are properly tightened, now it’s time to install the brake caliper, the lower fender and the clamp for the brake line. Don’t worry if the bottom of the four tube isn’t lined up properly. You can rotate this thing freely now that everything’s installed. The brake caliper bolts get tightened to 38 Newton meters, which is about 28 foot lbs. The small M6 bolts for the lower fender get tightened to three Newton meters, which is like two and a half foot lbs. I like to install red Threadlocker on all of these bolts here because these aren’t things I want coming loose later.

Now we can reinstall the front wheel and lower the bike back down. When reinstalling the front wheel on the F850GS, you tighten the axle nut to 50 Newton meters, which is about 37 foot lbs. And then you tighten down the pinch bolts on both sides to 19 Newton meters, which is about 14 foot lbs. Be sure that you alternate back and forth between both of the pinch bolts so that they both come down to an even torque.

This cartridge installation is now complete. If you want to learn more about products we make for your bike, please visit our website touratech-usa.com. And if you like this video and you want to see more like it, don’t forget to subscribe to our YouTube channel.