- Add Roll Pins to Lower Triple Clamp for Fork Gaiters
- Install Steering Stem in Steering Head
- Install Fork Tubes and Align Them
- Install Stock Fork-Fender Brace and Fork Sliders
- Install Telefix Fork Brace
- Instrument Bracket Modifications Needed For Use With Toaster Tan Top Brace
- Install Toaster Tan Top Brace
- Install New Steering Damper
Before I started this work I had completely removed all the front end components so I can have the frame powder coated, and I replaced the steering head bearings and rebuilt the front forks. You can read about this work here.
- 31 BMW 1977 R100RS Remove Front Forks, Handle Bars, Steering Stem, Fork Lock
- 31 BMW 1977 R100RS Replace Steering Head Bearings, Rebuild Front Forks
I replaced the stock top brace and steering stem nut with components from Toaster Tan. The stock top brace is not very stout and is easily bent causing the forks to not stay parallel in the X and Y planes. The Toaster Tan top plate is machined out of an aluminum billet, is thicker, and has a longer sleeve for the fork tubes to sit in.
The Toaster Tan steering stem nut has a longer skirt so there is more contact between the nut and the top plate. This combination creates a very stiff top clamp with much more resistance to flexing and permanent deformation so the front end behaves more predictably and fork stiction is minimized. All good things IMHO. 🙂
I used the following parts in this work.
|31 42 1 232 361||STEERING DAMPER||1|
|31 42 1 235 615||RUBBER GROMMET||2|
|31 42 1 232 241||BUSH||2|
|31 42 1 232 242||BUSH||2|
|31 42 1 235 620||RUBBER GROMMET||2|
|31 42 1 232 243||CAP||4|
|07 11 9 903 791||WASHER – 6,4||2|
|07 11 9 904 115||WAVE WASHER||4|
|TT-101||Toaster Tan Top Clamp||1|
|TT-301D||Toaster Tan Steering Stem Nut w/ Damper Hole||1|
|Install Bolts||Toaster Tan Top Clamp Mounting Bolts SS||1|
|07 11 9 985 070||TAPERED ROLLER BEARING – 28X52X16||2|
|31 42 1 234 509||RING||1|
A number of instrument bracket parts needed replacement:
- Large and small rubber bushings (part# 31 42 1 235 615 and 31 42 1 235 620)
- the chrome covers and lock washers on the large rubber bushings (part# 31 42 1 232 243)
- the steel bushings in the small rubber bushings (part# 31 42 1 232 241)
- the steel bushings in the large rubber bushings (part# 31 42 1 232 242) were found at ACE Hardware for pennies while the BMW part was about $11.00.
I also replace the steering damper and the steering head bearings and bottom dust cap.
- I used a glass plate from ACE Hardware and a tool from Cycle Works (FRONT END ALIGNMENT TOOL – DIAL INDICATOR W/JIG) to check the alignment of the forks in the X and Y planes.
- I used a vernier caliper to check the height of the fork tubes from the lower clamp.
- And I used typical shop tools.
Add Roll Pins to Lower Triple Clamp for Fork Gaiters
I cleaned and polished the lower triple clamp on the steering stem.
The 1977 R100RS did not come with fork gaiters but used a cap to protect the fork seals. This design leaves the fork tubes unprotected from rocks that can nick the tubes and that causes seal failure. So I’m going to put the fork gaiters on the forks. The top of the gaiters have a hole that fits into a role pin providing a passage for the air to move in and out of the gaiter as the forks move up and down. I found some at my ACE Hardware that will work (the hole is sized for a 5 mm roll pin) and install them in bottom of the lower triple clamp.
Install Steering Stem in Steering Head
The procedure for the 1977 R100RS is the same as for the 1973 R75/6 and you can read about how I do it here.
- 31 BMW 1973 R75/5 Remove & Install New Steering Head Bearings
These are the parts for installing the steering stem.
I generously greased the upper and lower tapered roller bearings with NLG red grease when I installed the steering stem.
The orientation of the top chrome dust cover, steering stem nut and steering stem acorn nut are shown below. The steering stem nut has a tapered end and that end goes against the chrome cover. Although this seems backwards, it ensures the nut presses on the inner bearing race to preload the tapered roller bearing.
Install Steering Stop Limiting Bolt, Washer and Nut
Due to the narrow width of the aerodynamic RS fairing, BMW limited the amount of handlebar rotation by installing an M6 bolt in the steering head (part# 07 11 9 904 505). I added a couple extra washers under the bolt head and nut on mine to shave a little more off the maximum left and right movement. When I rode the bike before taking it apart, I was unable to get the bars to stop scrapping the inside of the fairing.
Install Fork Tubes and Align Them
The procedure for the 1977 R100RS is the same as for the 1973 R75/5 and you can read about how I do it here.
Please read that material before continuing. I’ll point out the differences in what I did on the R100RS but I won’t repeat the procedure.
Setting Fork Tube Height
I align the marks I made on the fork tubes to identify the high side of each tube so both lines face forward when I install the tubes in the lower triple clamp. The stated distance is 160 mm from the top of the fork tube to the bottom edge of the lower triple clamp.
However, when I installed the Toaster Tan top brace as described later, I had to adjust the fork tube height to 161 mm to allow the sleeves in the top clamp to be at the right depth.
Checking X and Y Axis Alignment
This time I use the Cycle Works fork alignment tool with the dial indicator to check the alignment in the X-axis. I find the forks are in alignment in both the X and Y axis so I didn’t have to adjust them as I did on the R75/5.
I check the alignment as I add parts to the forks.
- After I install the tubes in the lower triple clamp and tighten the Allen head screws.
- After I tighten the Toaster Tan steering stem “acorn” nut finger tight.
- After I tighten the Toaster Tan pinch bolts with the sleeves installed.
At each step the forks stayed in alignment.
Here are two short videos showing how I checked the fork tube alignment in the X and Y planes.
Install Toaster Tan Top Brace
The top brace comes with two sleeves that go on top of the fork tubes.
It fit well on the steering stem and the fork tubes.
The center “acorn” nut fit tightly on the steering stem. I snug it down.
The top brace is above the top of the fork tubes.
Then I insert the two rings that fit on top of the fork tubes.
The two rings are supposed to be 0.7 mm above the top of the plate when resting on top of the fork tubes. Mine were recessed with the fork tubes at 160 mm so I increased the fork tube height to 161 mm to get rings at the 0.7 mm height.
Temporarily Install the Fork Sliders
The following hardware is used to attach the fork slider to the damper rod.
I use a bit of grease to install the small diameter aluminum washer from the fork rebuild kit on the threaded end of the damper rods. Then I install the fork sliders on the fork tubes carefully so I don’t damage the fork seals.
I use a small Philips head screw driver to align the damper rod with hole in the fork slider cap nut and push up on the slider until enough thread shows to install the wave washer and nut on the end of the damper rod.
I put a bit of anti-seize on the damper rod threads then install the wave washer and nut on the threaded damper rod finger tight.
Here are the sliders installed on the forks.
I insert the axle in the fork sliders to ensure they easily slides in the holes and isn’t binding. Here is a short video of how easily the axle should slide between the fork sliders.
Then I grab the axle and pull the fork sliders all the way to the top and drop them to estimate the time it takes for the lower to fall from being fully compressed.
Install Stock Fork-Fender Brace and Fork Sliders
The stock fork-fender brace has an edge with four holes which is the edge that faces forward. It mounts on the fork sliders using four Allen bolts, nylock nuts and wave washers.
It’s hard to install the stock fork-fender brace with the sliders on the fork tubes, so I remove the fork sliders and install the stock fork-fender brace with the bolts loose and then slide both fork sliders on the forks tubes being careful to not damage the fork seals. I I secure the Allen bolts with a wave washer and nylock nut.
The rear Allen bolts also secure the brake line brackets. The bracket fits on the outside of the fork-fender brace next to the tire, not between the brace and fork slider.
Before I install the fork sliders with the loosely attached stock fork-fender brace, I install the rubber fork gaiters on the fork tubes. The top of the gaiter has a hole that fits over the roll pin in the bottom of the lower triple clamp. I secure the top of the gaiters using the hose clamp on the boss on the lower triple clamp but I don’t install the bottom on the fork sliders so I can check for stiction as I assemble the stock fork-fender brace and Telefix fork brace.
With the bolts loose, I install the fork sliders on the fork tubes and tighten the nut on the end of the damper rod. Then I use a socket in my vice grips and an Allen key to tighten the nuts as described in the 1973 R75/5 write-up.
I want to test for any increase in fork stiction as I assemble the stock fork-fender brace and the Telefix fork brace. I put a little WD-40 on the fork tubes and wipe it up and down the tube to minimize fork seal friction. Then I pull the forks all the way to the top of their travel and drop them and note how long they take to drop to the bottom. This should take a second or less if the fork tubes have been aligned in the X and Y planes as described above.
Here is the initial test with the fork sliders installed and the stock fork-fender brace attached but the bolts not tightened yet.
Due to the sequence of events I installed the brake calipers prior to making videos of these tests. You can do these tests without the calipers but the fork sliders may slide a bit slower than in my tests. I cover installation of the disk brakes in this write-up.
I tighten the bolts one at time and torque them to 16 FT-Lbs. I grab the axle and pull the fork sliders to the top and drop them to see if the stiction increased. On the last bolt, left rear, the stiction went up. I loosened that bolt and can see a narrow gap between the brace and the inside flat of the fork slider.
I use a thin washer and insert it into the gap and then tighten all four Allen bolts one at a time testing the stiction after each one. I don’t detect any increased fork stiction.
Here is the test with the stock fork-fender brace Allen bolts tightened.
Install Telefix Fork Brace
Before installing the Telefix fork brace, you have to install the front fender due to limited clearance between the top of the fender and the bottom of the fork brace. I show how to install the fender in this document:
After I removed the Telefix fork brace, I cleaned it up. Here are the parts.
I found instructions for installing the Telefix fork brace on-line and down loaded them. Here they are.
If you turn the brace upside down you can see numbers on the outer and inner fork tube clamps. The numbers on each part should match on each side of the brace.
The center bracket is made up of two pieces bolted together with two large Allen bolts. I loosen the bolts so I can slide the pieces in and out.
I tilt the center bracket so I can slide it between the fork tubes and then onto the top of the fork slider so the groove in the bracket rests on top of the slider. I leave the two large center bracket Allen bolts loose.
The outer half of the fork slider clamp fits on the outside of the fork slider and is secured to the center bracket with four small Allen screws.
I put some blue locktite on the small screws and finger tighten them on each side.
I snug them up to 4 FT-Lbs or 48 IN-Lbs using my inch-pound torque wrench in increments ins a cross-wise pattern so the gap between the outer and inner halves is even.
I check fork stiction as I get each side tight. I find that if I tighten the four small Allen head bolts too tight fork stiction goes up. By experiment I settle on the 48 IN-Lbs value. The Telefix instructions don’t provide a value but mention “lightly” as the tightness of the bolts.
When both sides of the bracket are secured to the fork sliders and I don’t detect an increase in fork stiction, I tighten the large center Allen bolts alternating between them in increments so they don’t tweak the fork sliders. Again, if I tighten these too tight, fork stiction goes up.
The instructions say to loosen the two large Allen Bolts 1/4 turn and push the forks up and down several times before “lightly” tightening the two large Allen bolts so I will have to do that later and at that time I’ll put some blue locktite on the threads.
With the two large Allen bolts snugged I test the stiction as shown in the following video.
Instrument Bracket Modifications Needed For Use With Toaster Tan Top Brace
I remove the Toaster Tan top brace now that I have the fork sliders installed and have ensured the fork tubes are parallel in the X and Y plains, the axle slides easily into the fork sliders and the stock fork-fender brace and Telefix brace are installed without any increase in stiction.
Handlebar Bracket Modifications
The top plate has four holes that allow the handle bar brackets to forward or a bit more backward depending on which set of holes the brackets are installed in. But the Toaster Tan top brace is thicker than the very thin stock BMW plate. Therefore the stock studs installed in the handlebar clamps have to be removed and longer Allen head bolts supplied with the top brace are used to attach handle bar brackets from the bottom of the Toaster Tan top brace.
I use a rag to protect the handlebar top clamp and put them in the rubber jaws of the vice. I use two nuts and lock them together than unscrew the bottom nut to remove the studs from the handlebar top clamp.
Instrument Bracket Modification
If you move the handlebar clamps to the rearward set of holes, then the instrument bracket front holes are not secured by the handlebar clamp and additional bolts have to be installed to secure them. Since I want the handlebars as far back as I can get them (I’m not 20 any more and neither is my lower lumbar muscles 🙂 )
In addition the instrument bracket may not fit the slot in the bottom of the Toaster Tan top clamp and mine is one of those that is too wide to fit.
The fix for this is to grind the outer edge of the instrument bracket to allow it to slide into the bottom slot.
Install Instrument Bracket Hardware
I got new rubber grommets and several steel bushings as some were missing when I disassembled the instrument bracket. I also picked up some bolts to use to secure the rear of the instrument bracket to the Toaster Tan top brace.
I insert the rubber grommets and steel bushings into the instrument bracket and test fit the bracket to the bottom of the top clamp in the most rearward position to check alignment.
Instrument Bracket Mounting Hardware Modifications
Here is the mounting detail of the smaller rubber grommet with the bolt (M8-1.25 x 30) I used to secure it to the Toaster Tan top clamp.
When the instrument bracket mounts to the top clamp there are two metal caps that on the top and bottom of the large rubber grommet.
When the instrument bracket mounts to the top clamp there are two metal caps that on the top and bottom of the large rubber grommet.
But when using the rearward holes in the Toaster Tan top brace, the metal caps interfere with the holes. And, when using the Allen bolts supplied to mount the handlebar clamps the bolts are too long since they don’t go through the large rubber grommet. So I have to make some modifications.
In the following work, I show adding two steel bushings for the alternate rearward mounting hole. This is NOT necessary. By the time I ground out the bracket holes large enough for the bushings, there is now enough clearance for the Allen head bolt cap. So I removed these bushings when I later added 1″ risers to the handlebar clamps as all four Allen bolts I used here were now too short. I’m leaving the section here since I had to grind out the circular hole in the bracket so is big enough to allow the Allen head bolt to fit, and you can see how an idea one thinks is a clever way to solve a potential problem sometimes turns out to be unnecessary when you finish doing the work 🙂
I got two more of the steel bushings I bought at ACE Hardware for the large grommet. These are sleeves that are close to the same thickness as the rubber grommets with the two metal caps so they will take up the extra length of the Allen head screws supplied by Toaster Tan. But, they are a larger diameter than the original BMW handlebar clamp studs, so I have to grind out the semicircular hole in the instrument bracket and modify the metal caps on the large grommets to get them to fit.
I use some Dremel bits to do the grinding.
Here is how the Allen head bolt and the sleeve fit after the modification.
Next I cut out a notch in the metal caps so they will clear the metal bushing.
To prevent rust on the areas I ground, I apply some black touch up paint.
Now I install the other Allen head bolt (M8-1.25 x 30) through the large rubber grommet to secure it to the Toaster Tan top plate.
Here is the instrument bracket secured to the Toaster Tan Top Brace.
Now I mount the handlebar clamps from the bottom using the Allen head bolts. Everything fits 🙂
Install Toaster Tan Top Brace
The top brace and instrument bracket modifications are finished and the forks have been aligned and assembled. I install the Toaster Tan top brace on top of the steering stem and fork tubes. I don’t want to tweak the fork lower triple clamp or the fork braces when I tighten the Toaster Tan steering stem acorn nut.
I use a handlebar in one of the handlebar clamps to act as an anti-torque lever. By positioning the handlebar in my stomach while I torque the nut, the forks don’t push against the fork stops which can misalign the forks.
I insert the top brace spaces on top of the fork tubes and then finger tighten the acorn nut to push the top bace down all the way. I torque the top pinch bolts on the Toaster Tan top brace to 15 FT-lbs to secure the brace on the fork tubes.
I modified a 36 mm socket to remove the beveled on the end. That allows the socket to fully engage the flats on the acorn nut and the fork tube top nuts.
I torque the acorn nut to 80 FT-lbs.
Here is the Toaster Tan top brace with the acorn nut installed.
I’ll use the same handlebar anti-torque technique when I torque the fork tube top nuts, but I’m going to wait until the new forks springs arrive. When I measured the length of the original ones they had sacked by more than an inch.
Install New Steering Damper
I had the steering damper bracket powder coated. Here is the cover, the internal parts inside the cover and damper adjusting shaft.
The bracket has a finger and spring that pushes the finger into detents along the side of a sliding metal rack. The rack has gear teeth and engages with teeth in the damper adjusting rod. As the damper knob is turned, the it turns the damper shaft which then pushes the rack inside the channel of the cover until the finger falls into a detent to hold the rack in one of three positions.
Here is how the pin and spring fit in the cover.
I grease the rack plate and put it in the track of the cover.
The damper shaft teeth fit into the teeth of the rack plate.
Before I install the damper rod into the rack plate, I make sure the flat on the top of the rod where the steering damper rod mounts is facing to the rear. When the shaft is in that orientation the steering damper knob is at the “0” position, which provides no damping. That means the ball in rack plate is at the center of the cover.
I push the rack plate so the ball on the end of the rack is in the center of the plate, insert it over the damper rod and then secure it with the two Allen head bolts.
Then I insert the rubber grommet over the damper rod that secures it in the hole in the Acorn nut and then the steering damper rod.
Here are the parts that attach the steering damper to the frame and the ball on the end of the rack pla.
I install the ball that goes on the bracket on the frame.
The damper attaches to the two balls with the fat part of the damper at the front.
Each end of the damper has a cup that fits over the ball. I grease the ball before I press the cup over the ball.
The cup is secured so it won’t come off the ball with a wire clip. The straight end fits into a small hole on the side of the cup The clip is rotated so the round end snaps around the base of the cup.
Here is the installed steering damper.
I have to install the new fork springs, rork oil and torque the top fork tube cap nuts, but I’m going to wait on that for a bit.
2017-08-06 Note added about NOT needing bushing for the handlebar clamp bolt.
2017-08-07 Added steering stop limit bolt install.
2020-05-18 Minor edits.