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1990 R100G/S

1990 R100G/S Franken Project

The Making of ...

Where it all started ...
Second thoughts on the project
Timing Chain
Cylinder and Pistons
Cylinder and Pistons (again)
Fitting a monolever swingarm to a GS frame
Monolever swingarm extension
Second round on sourcing
Digital Cockpit
Connection Rods
Triple Trees
Electrics and Wiring Loom
Exhaust System
Assembly starts
Maidentrip and finishing up
Maintenance Log

May 2006:
I was always dreaming of building a Frankenbike with the "Best Of" 33 years Airheads, 1969-1996. Here is what I have acquired so far:

GS frame and subframe
complete GS Front End
a 1983 R80RT frankenbike
miscellaneous parts to make a complete bike

Here is a description of all parts so far:

July 30, 2006:
I am not exactly sure where this project is heading as it has not really started yet. But it already looks like something.
August 20, 2006: Toughts on the project
Where is it heading? I am starting to get the general idea: a R100ST is what I am trying to build here. The GS frame gives me the opportunity to go offroad with a different set of wheels/tires. I will be having a monoshock swingarm with a 37:11 final drive, don't need speed here in Northamerica, I am more of a "torque" person anyways. I will use a GS rear hub with an 18' Akront/Sun or Excel, the front will be a 19' rim on a GS hub. Tires: I guess I will go for slightly wider tires, 100/90-19 in the front and 130/80-18 in the back. GT501's are a preferred choice, something that sticks. 2.15' wide rim for the front, up to 3.50x18 for the back, laced to the GS hubs by the folks at Woody's Wheel Works should do just fine. That, together with a Wilbers/Oehlins supported monolever swingarm and the GS front end with progressive springs (or better a RaceTech 'Gold Valve' cartridge emulator should guarantee a very nice and solid chassis. The subframe will (or may) be a modified /7 subframe to get the hinged seat pan working. Might as well be a GS sunframe. A Corbin gunfighter will be my choice (just because I have one!).
December 2006:
Things are moving along and the fact that I acquired a blue-white windshield, white headlight housing and fender (featuring the 1988-1990 Alpine White/Blue Scheme Code 642) had a lot to do with the decision to build the bike as a G/S with a blue-white colour scheme:

Mind you, a 1991 R100GS never had a monolever rear end, so I am going to dubb this newest project of mine in good ol' BMW tradition:


When it is finished, it should very much look like this 1990 Alpine White Color Scheme (Code 642), except for the exhaust (which is planned to be a stock BMW 2-in-2) and the rear suspension which is based on a monolever, the color scheme is the 1990 Alpine White Scheme Code (642).

Spring 2007: Second thoughts on the project

August 2007: The fun begins ...

I am tackling the engine first: after a quick rework of the carbs, back last year, I had the engine running. It wasn't running too bad, a little rough but I did expect that because it wasn't properly tuned.
Checking the timing chain is my next task. I expected it to needing replacement, the condition I found it in certainly supports that:

Here is my opinion and way forward based on the findings: The engine was stripped down anyways, so let's prepare for the operation and get the patient on the bench, strap him down and get the Dremel ready:

I got a 3-jaw 4in Bearing puller and removed first bearing and the crankshaft gear:

The crankshaft gear isn't completely toast yet, but is being replaced. The chain is knackered, as you could see on the above video. Got myself a drift, a 1 1/2 x 3 in steel pipe, availabIe in Home Depot's plumbing section. Heat up bearing and crankshaft gear, a bag of ice to cool the crankshaft and the job's half done. I did not support the flywheel center, so I might have buggered bearing and thurst sleeve completely ... but I do'nt think so.

The whole procedure didn't take longer than 30min. The below is my way of dealing with the masterlink: connect both ends from above with the old masterlink, install the new masterlink from the rear (watch those openings, that is where these things disappear in the engine cavities!) and assemble coverplate and C-clips:

Next thing was loking at heads, cylinders and pistons: Next on the list is the clutch: it was very difficult to remove. t first it wopuld not budge, even soaking and a mallet would not help. In the end, I had to pry it off: The flywheel teeth look hardly worn as well, which points to a low mileage engine. I cleaned the clutch parts up to see whether they can be reused:
I looked a bit more closely at the pistons and wrist pin bores:

I guess, that is for the barrels and pistons!

End of September, I got lucky on eBay Germany with a set of barrels off a 1979 R100S with 80.000km (50.000mls) and a set of matching 9.5 pistons. The seller was willing to ship to Canada, so they are here:

Very good condition of both pistons and barrels, no scoring inside, very smooth, could turn out to be a very good deal.
December 2007:

I am looking at the tranny from my 1982 G/S that got busted during my 2006 Transamerica Trail Trip: completely scrap, said Bruno. The gearbox has a kickstarter which can be of help in emergency situations. I decided to give it a complete makeover (I leave that to the experts: Bruno's Machine and Repair) and have it modified to the latest design plus add one significant improvement:

This new gearbox should be quieter with easier shifting and subsequently reduced wear. We will see about that!

Added March 2008: Since I will not be using a stock speedo, a little gimmick is needed to first, close the opening and second, provide more generous venting without getting the tranny flooded when submerged:

The 1990 GS frame was intended to be fitted with a monolever shock and swingarm, like the 81-86 G/S. I used a 1987 monolever RT swingarm and had a very sturdy bracket welded to it. Since I had my gearbox back from Bruno's it was time to dry-fit the swingarm to look at various things: So I fitted swingarm and a dummy (K100) shock and found that the swingarm is angled a lot more than stock. To the extend that the u-joint grinds in the swingarm! What's going on here?

So, off on ADVRider I went to get dimensions as I sold my own 82 G/S a couple of weeks. Thanks to woodgrain and TEXASYETI, I was able to find the problem. A couple of sketches first.

I did not realise that the top shock mount location of the 88-95 GS was about 30mm (1.25in) lower than the 81-86 mounting point. What did that do to the lower shock mounting location: it needs to be moved by roughly 25mm! I used the good old papermodel to visualise:

What does that mean in plain numbers:
88-95 RxxxGSDescription81-87 R80G/S
46mmUpper shock mounting hole to top of bracket "a"22.34mm
55mmUpper shock mounting hole to frame (rear of tube, measure tangential) "b" 54.25mm
76mmOverall bracket length to the joint with frame "c"78.40mm
302mmDistance from Bracket (joining the frame) to center pivot bolt "d"309mm
260mmDistance from upper shock mounting hole to center pivot bolt "e"287mm
312mmDistance from bracket outer end to center pivot bolt "f"314mm

Now, let's use some more sophisticated way of showing the difference:

Learned something new today!

Fitting a monolever swingarm to a 1990 GS frame is one thing, extending the swingarm at the same time another. I deemed the extension necessary, because the (GS) paralever swingarm is 35mm longer than the monolever of the G/S. That alone, with a stock GS front end, would lower the rear end. Therefore I decided to extend the swingarm moderately by 30mm. I calculated the force at the swingarm pivot point to increase by about 30%. Since the Paralever GS uses the same frame, I am taking my chances and not reinforce that area on the frame. At the same time, the extension also requires a 17% higher spring rate of the rear shock, because of the change of the levers and dynamics. I found the formulas on the internet.

Now that I knew what needed to be done I started work on extending the swingarm which turned out to be pretty easy: I had an adapter fabricated (rather than cutting the swingarm and welding a piece of tube inbetween):

I considered the lower shockmount pretty flimsy and had this mount modified with real metal bracket rather than 'folded' sheetmetal:

Next up was the driveshaft, a much more difficult undertaking: my machinist had basically two ideas:

  1. Shrink-fit, pin and weld an 'outer' sleeve
  2. Shrink-fit, pin and weld a 'male-to-male' spacer

Unfortunately our first attempt, the outer sleeve was interfering with the diminution of the swingarm and could not be made to work.

Our second attempt was the male-to-male spacer method and obviously that worked perfectly. So, as per the above drawing, a shrink-press-fit was used as means of interconnect with vent bores for the air trapped inside before the spacer is pressed in. The spacer was then pin'ed and welded. The whole assembly was smoothed out on the surface so that no sharp corner or edges from the weld beads exist. Looks like it was never touched. Unlike the HPN solution, the cush drive was maintained. Radial runout was measured before and after, the driveshaft runs true.

It is very likely that this method will work on 2in or 4in extensions just as well. Whether it will hold up in real life remains to be seen but I am very confident that this won't break or shear.

Now, it was time for dry-fitting: first the swingarm with the near rear wheel (laced off-center by 1/2in) and the wide (126mm) wide tire ... perfect, every thing fits as planned. 8mm clearance between tire and swingarm, great!

Next, dry-fitting everything with the swingarm extension ... ouch, the tire rubes the swingarm! Hu? Upon closer inspection I realised I did not take into account the change of shape of the swingarm to accommodate the cush drive. So, the tire was rubbing there. Again, my machinist had the right idea: a piece of the swingarm was cut out and a steel plate welded back in. That fixed the problem.

Now, here we have the finished result:

Clearances are perfect:

January 2008:

Still sourcing parts:

Worked on a couple designs for the planned digital cockpit (click on image for original size pictures):

Checking the connection rods (conrods):
To get them off you need a special tool: a long XZN socket #10 (I just bought the key, it fits a 10mm socket!), click here for Hazet datasheet, available at good hardware stores, Jeff on ADVRider sells them too: http://www.northwoodsairheads.com/Tools.html.

It is fairly easy to remove the conrods: just loosen the bolts (use new ones for assembly), wiggle out the conrod (two locating dowels!) and mind the end cap (clamp):

The bearing shells can be carefully pried out, no excessive force, just a little help at the locking tab:

When you click the pictures to see details in high resolution, you will see that one pair of bearing sheels has light scoring, the other looks worn, but in a weird way, it almost looks like pitting. I will replace both.

I also measured the big and end and small end and compared it against the spec.

ConRod Big End I.D. less bearing shell (2 measurements 180� apart)ConRod Small End bushing I.D. (2 measurements 180� apart)ConRod Width (6 measurements in 60� increments)
Specification 52.00 - 52.01522.015 - 22.020 (max 22.040)21.883 - 21.935
Specification 2.0472 - 2.04780.8667 - 0.86690.8615 - 0.8636
ConRod Left measurements52.00, 52.0222.05, 22.05.8625,0.8625, .8615, .8625, .862, .8635
ConRod Right measurements52.01, 52.0222.05, 22.05.861,0.861, .8611, .8615, .861, .861
Initial decisionOK to only replace bearing shellsreplace both bushingsOK, no actions necessary

The new small end bushings were machined to fit the wrist pins, very snug fit at around .006 clearance:

Woody's Wheelworks did an amzing job on the rear wheel (17x2.50in Excel rim laced 1/2in offcenter to stock GS rear hub) and the front wheel (21x1.85in Excel rim laced to stock GS front hub).

The Kenda 761 Dual Sport is 127mm wide which will clear the swingarm just fine (Metzeler Enduro 3 is 113mm) as the rim is laced offcenter a bit less than 1/2in. Dry fit to follow when the front wheel arrives.

Click on pictures for higher resolution ...

Banged up triple trees:
Back in 2006, I bought a (supposedly straight) Airhead GS front end including wheel/brake rotor/caliper/etc from a Bumble-Bee from Germany, which was originally intended to be used on the '82 R80G/S that I refurbished at the time. That never happened, I kept that bike stock.


Now, they will be used on this project, meanwhile de-Bumble Bee'd and all new plastic parts and bushing in conjunction with a Race Tech Gold Valve, but that set aside, my first dry fit was a disaster: the fork tubes were running out badly about 1/8in at the bottom. That triggered me to inspect the lower triple tree very carefully and low and behold, one steering stop was severly damaged, not yet sheared off, but close. Now what?

Well, time to visit my friendly local machinist Richard and he had the right ideas:

First, he took the steering stem as a reference and created a new plane perpendicular to the stem and machined it accordingly. With that new reference, the tube bores were rebored and oversized to accept a sleeve.

Overall, a painless exercise, it created a perfect fit for the tubes and ensured their parrallelity (?) in both X- and Y-plane. It remains to be seen what happens when everything is back together. It should be a perfect fit though.
Electrics and wiring loom:
Having had the pleasure to help others (and myself) out on the road, I have thought long about how to equip the bike (especially when it comes to backup) and here's how: Hardest part is to get all parts mounted in a tidy manner. The Xenon ballast is very small und will fit behind/underneath the headlight, all other parts have to fit underneath the tank: First I thought of a very simple solution:

A bit of a bath tub, don't you think? And don't I need some air to cool there ... not good.

What if I took some aluminum, JB Weld and rivets, fabricate some brackets and see how far I get? The aim is to integrate the three existing brackets that are welded to the backbone, so that a solid platform exists for the parts to be mounted.

I have finally received my coils, added some more bracketry, aluminum rivets and JB Weld and completed the dryfitting:

I accounted for everything and somehow I will find the two spots for the additional AUX relais (horn and aux power). Note that this setup also includes the 14.5V voltage regulator, which (together with the diodeboard) is the backup for John Rayski's recitifier/regulator combo.

This setup is baseline and intended for use with a dual electronic ignition. Should that fail, I use the points as a backup, combined with 2.6Ohm low energy coil in place of the Dyna coil:

Now, the model goes to my favorite machinist to make something more professional ... although, that model would probably be good for a year!
Dry-fit of luggage carrier and bags, just in case I ever wanted to go with cases on a street-only ride ...

Exhaust System:

A lot of interesting things can be done with a R100R exhaust on a G(/)S, such as this ...

... or that!

Underneath the chrome covers, there is a full stainless steel exhaust. The front chrome cover can be easily removed by drilling the 4 rivets out. The brackets come off with a Dremel tool, some polishing and off you go. Can be mounted to the GS canister if you remove the big bracket.

When using with the R100R canister the GS centerstand now clears the exhaust, due to a very convenient design (see the big "chamfer"?):

Now, the rear chrome cover can be removed as well, just like in the second picture above, saves another 4.5lbs.

I am already past stage 1 (removed front cover and polished) and will be utilising this as a low exhaust to run equal size bags (and to experience that low frequency 2-in-1 rumble from what was originally a K1 / K-16V exhaust). I would like to attempt to remove the rear cover as well. I am even contemplating to get a GS canister and run the exhaust high or low, depending on the mood of the day (or whether I need bags or not).

I did not know that the HPN Baja exhaust is based on the R100R muffler, in a different "package".

Assembly starts:

A couple of notes taken during the assembly phase:

A couple of notes with regards to heads, pistons and barrels: I received my re-conditioned heads back from Bruno: A work of art!
Seats were fine, guides and valves were renewed and the heads dual-plugged, one spark plug thread and both valve cover stud threads needed Helicoil. The guides were actually slightly shortened to support a high lift cam (if I ever wanted to do such a modification). Both heads were skimmed to remove warping, leading to an approximate increase in compression of 0.2.
I also measured barrels and pistons, actually with not so desired results:
The pistons from the 1980 US R100CS (8.2:1, stamped 93.98) measured 93.95mm with no wear/abrasions, the 1977 pistons from the 1977 R100S (9.5:1, stamped 93.96) measured only 93.88, but showed no wear at all. The barrels of the same bike (1977 R100S) measure 94.0308 on average. The taper on the barrels is more than 0.1mm with only a maximum 0.08 allowed. Ovality is most certainly more than allowed. The ring end gaps will be just about in spec. The piston clearance of the high compression piston does not scare me, on the contrary, it will help the heat transfer on the high comp pistons. So, high comp pistons it is, although the measurements and tolerances would certainly favour the low comp pistons!
I will however count on German ingenuity (and design margin) to run the new rings in and get at least 30,000 to 40,000 km out of this combination.

Addendum August 2008: After engine break-in and the first 500km, the compression values are 10.25 and about 10.6, so very close. The absolute values are incorrect, as I did not remove the Bings for the test. At some point, I'll do a leakdown test ... if I can find 100psi!

With the heads being back, first thing I did was dry-fitting the R100R exhaust with the all chrome covers removed: looks great. With that being a GO, I fitted rear swingarm, suspension. I bought some 21x36x2.5mm nylon washers to fill the gaps between the swingarm bearings and frame so that they don't get washed out in rain. Finally I set up the relocated brake rod and cleaned up the workplace for the more delicate work on the engine, which requires a bit more cleanliness!

The bike is slowly starting to look like a bike again, especially with that bad-ass 9" headlight that has a XENON HID conversion kit. Let there be light!

My thoughts and resulting activities on engine balancing:
We are looking at 1230g of metal, unevenly distributed amongst connection rod, wrist pin and piston. The big question really is whether a 5g (or 0.4%) mass difference between left and right side makes a big difference? Most people say it does, but who knows whether they synchronized the carbs at the same time or whether other changes came about.
Let's talk about Moment of Inertia first: Moment of Inertia is a scalar (a number), with dimensions of distance squared times mass. Moment of Inertia is a property of rigid bodies. Being a scalar, it is additive, so that the Moment of Inertia of a composite body is the sum of the Moments of Inertia of its parts (relative to the same axis). That, in my mind applies to the conrod+piston+wristpin assembly. Poses a question: do all elements need to be perfectly balanced or can the whole assembly be?
Furthermore, inertia loads are both compressive (crush) and tensile (stretch). To better understand, lets look at those 2 assemblies without the combustion process. When the rod is pulling the piston down the bore from TDC, the mass of the piston plus any friction caused by ring and skirt drag imparts a tensile load on the rod. Once the piston reaches BDC, the dynamics shift. Suddenly the rod is pushing the mass of the piston as well as the friction load back up the cylinder bore, and a compressive load on the rod results. Then the piston stops and reverses direction to head back down the bore, so the inertia of the piston, once again, tries to pull the rod apart as it changes direction.
Does that not mean, since there's only a "simple" push-pull operation that that the weight distribution doesn't matter, as long as the masses are on the same axis? I am deliberately counting the circular crankshaft motion out, as I don't think it matters much in the scenario.

I believe that since all individual masses are on the same axis, the distribution of masses along that axis in first approximation doesn't matter much in the case of that push-pull operation of a "reciprocating engine", a.k.a. Airhead. Equal reciprocating masses are reducing vibration, reducing the overall mass would increase the overall improve performance. I don't think that balancing each individual component makes a huge difference, the crankshaft pushes against piston ring friction and inertia (which is additive along the same axis).

Subsequently I separately balanced conrod+wristpin+piston assemblies, and bolts+conrod clamps to be of equal weight, within 0.1g. The pistons itself were within 0.9g of each other already.

I removed about 4g of material in total.

Now we're getting somewhere. 2 years and 2 months after the idea was born and the first part bought, I am only one week away from the maiden trip of my 1990 R100G/S. I will have to run the dented GS tank a while to figure out which of the two seats (Solo or Corbin Gunfighter) fits my butt best. Very excited but also worried if everything will work out as planned:

Not much longer ...
More labour followed in July to get the motorcycle fit for the maiden trip which took place on July 19, what a glorious day (and a long wait):

Staring with the good news: that 1000cc engine with the high final drive ratio is a dream, powerful and pulling like a train (running in single plug mode only for the time being). I already know that I like it. The charging system pulls out 13.8V, very good start. All electrics works as they should. The R100R exhaust goes very well with the engine and suports its torquey characteristic even more, a brilliant choice. As expected the 1.25in swingarm extension over the stock 1981-1987 G/S are noticeable, it needs a wee bit more persuasion to lean. So far no other noticeable sideeffects. There are no rattles, no noises, no whines and the engine oil after 50km hard brake-in was clear. The clutch has turned out nicely too, despite the pitted surfaces: full pull in all gears and no slippage. I couldn't have been more happy about that. What remains to be done is fine tune the engine, install the OMEGA ignition (switch to dual-plug configuration), set up the suspension and as a final touch, install the BMW Speedster windscreen. See if that provides enough wind protection in the end. If not, I'll just get that National Cycle Deflector Windscreen.

As to the bad news: the rear brake rod relocation was a complete failure! In fact one can't even use a brake rod in that location: the earlier G/S had the pivot points of swingarm and brake rod so close to each other that swingarm movement would not cause a braking effect. Now, in 1988, BMW changed that area to accommodate torquearm support and a stiffer structure with a small cavity behind the footbrake lever for a rear micro brake switch that is more up-to-date. In the course of that design change, they had changed to a brake cable, as swingarm pivot point and brake cable rear pivot point were a lot further apart which makes those two pivot points and the rear brake lever work in a parallelogram: the swingarm moves up -> the rear brake lever turns slightly causing the rear brakes to be activated. Back to the drawing board it goes for implementing the brake cable. The other nuissance was a seeping right cylinder base. Two sealing attempts were necessary, with the final answer being using RTV rather than Hylomar. But I might have jumped the gun here: I don't think I read the Hylomar fineprint ... ever. It suppossedly says to apply and wait until its tacky. I never did.

Revised rear brake configuration:

Obviously, I need to marry the 1988-on rear brake cable with the pre-1988 final drive to make the brake function independant from the swingarm action. Not a difficult undertaking, just requires another custom bracket as can be seen on the center picture above. I am sure my machinist will change that design for better manufacturability but that is basically it.

Top of page ...

Season 2008 pictures

Adding the windshield and finishing the cockpit (Aug 08):
I finally attempted to fit the R11x0R Speedster windshield that I acquired ages ago. I used the same principle (stand-offs) as I did before on my R80G/S (that I do no longer own):

At the same time, I added the GPS and finished the cockpit:

I am satisfied with the work and will see how it holds up in the Colorado mountains later this year.
A fellow rider pointed me towards a potential problem with my single beam headlight: what if it fails at night leaving me literally in the dark? I had thought about a set of real cheap driving lights, but for a different reason: visibility during the day. But running 2 x 55W constantly in addition to the 35W of the HID just isn't working, even or just barely with the BMW 280W alternator.
However, the idea of sitting in the dark on the trail (or anywhere for that matter) because of a failing headlight or headlight relais made me rethink my initial decision:

Now, naturally one would use power coming from the headlight to run the driving lights. But what if the headlight relay fails? In order to be completely independant from the headlight 12V supply, one has to run the driving lights off a different source altogether. For reasons of available power, I will run the driving lights only at dawn/night (when it is crucial to have a light) and decided to get the power through my rear auxiliary power socket. Just plug it in when needed ... problem solved.
In preparation of the Fall trip, I mounted the Krauser/Hepco&Becker luggage carriers. They are intended for the 88-95 RxxxGS with low exhaust conversion and support same size bags:

One 1700mls trip to New England, trip report here: Fall 2008 in New England

One 5000mls trip to KS/CO/NM/TX/OK, trip report here: Grand Fall Ride 2008

Winter 2008:
I had new tires put on in a local shop and the mechanic noticed a crack in the rear rim, just at the weakest area between the valve stem hole and the nearest spoke hole:

It looked like a material problem to me (Excel), so I contacted the guys at Woody's Wheelworks who put the wheel together for me about 7700mls and 11 months ago. Remember, it was a design featuring a 1/2in offset to the left to allow 130 tires (Airhead GS sizes) in a monolever swingarm. Zach at Woody's was very helpful: his first assessement came down to an excessive stress of the particular area due to two facts: the rim design (non-dimpled, about 5mm rim thickness at that point) and the stresses induced by offcenter cross lacing. He had never had this problem before, but then, this is the first time he tried this kind of application. We are still communicating the best course of action but it might be necessary for me to go back to a configuration similar the 1981-1987 stock design, but using a 2.50 x 18 rim, either x-laced BMW OEM (oilhead GS) or centerlaced Excel. There is a certain advantage to it in another area: to compensate for the smaller rear wheel and tire aspect ratio, I had the (1988 GS) front forks height-reduced by moving them about 1in further through the triple tree, thus reducing its travel as well. So, going back to an 18in wheel would eliminate that restriction too.

So first, I figured out the availibilty of 18in rear dual sports tires. The results were encouraging:

Then I looked at the effect of bike geometry when changing the rear wheel. I found this website (U.S And Metric Tire Size Information Calculator) and compared a 130/80-17 with a 120/90-18 (TKC80, D606):

A 18" rear wheel with a tire sized 120/90-18 would be about 1.3in larger in diameter than the current wheel, raising the rear about 0.65in. The front will have to be raised accordingly to maintain the bike's rake, trail and wheelbase.In comparison, the 120/80-18 is just about the same height then the 130/70-18.The tires noted in bold letters are rasing the rear notably. I am sure the 1993 exhaust collector has to be dented to make space for the larger rear wheel.

Another possibility is the use of a dimpled rim that is reinforced in the area of concern. I am waiting for Woody's confirmation.

Update on cracked rim:
The crack is indeed a result of stresses induced to the rim by offcenter lacing which puts additional loads on the rim as the hub is originally designed for X-lacing (BMW OEM) so the spoke holes are directional. There would a dimpled rim available but Zach @ Woody's was more or less suggesting not to do it again unless I NEED the additional clearance to the swing arm.

I don't.

I also looked again very carefully at the hub design which really supports X-lacing best, due to the directional spoke holes as mentioned before.

Based on the above, I have decided that I will have the rear wheel repaired using a (front R100R) X-lace 18 x 2.50 rim that will be laced slightly offcenter, something like 1/4in or thereabouts, just to get some additional clearance for knobbies. That'll put my worrying mind to rest: BMW must know something and the X-lacing has some merrits.

On a positive note: using 120/90-18 tires I will result in more than 1in additional clearance in the rear, so I will be able to raise the front as well by 1in (the amount the forks are currently extended through the top triple tree to account for the smaller 17" wheel).

Last year, I bought a BMW stock R100R 18" front rim. Admitted, it was an impulse buy then. Now, that 18in R100R front rim is laced to my rear GS hub, thanks to Woody's Wheelworks. It raises the rear nicely so that the front can follow (which is still 2in lowered). That 18in rear wheel requires a 1" dent, yes a huge dent in the R100R collector so that it can be mounted. My machinist is taking care of that.

The parts finally came back and as usual, the workmanship was excellent and the hours of preparation and measurements paid off:

The Kenda 270 that is currently mounted is a 4.50 x 18 with 121mm (4.76in) width and 27in diameter on the 2.50 x 18 rim @ 32PSI tire pressure. Clearances are as follows:

You also know that I am still not happy with my rear brake setup: deep bumps still activate the rear brake. Hwere are the three design that didn't work to my satisfaction:

I'll try something else now, my machinist is working on it.

That'll do. It is as close as possible to the original rear brake cable routing on the GS.
This season (2009) I will be running a 32:10 (3.2) rear drive as opposed to the shorter 37:11 (3.36) that I ran 2008. I hope will improve gas mileage and reduce highway rpm.

I have another rear drive, a 33:11 (3.0) in the works that should reduce rpm by another 7%. That is in pieces with Bruno, who will refurbish it to as-new condition. Try-out -> probably next year.

Meanwhile I installed the new alternator stator and rotor (both parts from Rick Jones) to run that combination this season. I have decided to swap over the entire charging system once a year and run them alternatively and keep the other one as a backup.

I have bought the (ridiculously) hi-viz roadcrafter tank panniers (8l each side) to shift weight (especially spare parts) from the rear to the front and for better accessibility. They are really yellow!

I discussed my Ohlins shock with a local guy, especially the fact that I needed 34mm pre-load without luggage and nearly maxed-out the pre-load at 45mm with load. We established that Kyle USA (although they had all the data) did not set it up for me, can you believe that? It has a 70kg/mm spring installed (which is stock at delivery) whereas I should have had a 95kg/mm. John Sharrard from Accelerated Technologies in GTA swapped the spring (charged me only $50 for the spring and took mine as a trade-in) and then lengthened the shock by 3mm. He noticed that the oil was filthy and dirty! WTF? Did that Kyle guy do anything? NOPE! So I spent another $150 on setting up the Ohlins. Am a happy camper now.

Nuts 'n bolts: I thought I'd use high strength plain finish (black) bolts and stainless where it doesn't count, but they all rust badly on the surface. Even the stainless type A2. Only the A4 stainless is holding up. Doesn't look good, hurts my eyes. So, I put another set of zinc/yellow zinc plated screws, washer and lockwashers together and will install that at rear subframe, the entire front end and the covers.

The fork gaitors were shot when I put them on, they still are. I have original replacements and will put them on before the season.

Will also put the marine type ignition switch in that I bought. Three positions: OFF, IGNITION ON, LIGHT ON

I have bought a new stainless steel brakeline locally, C$43 shipped. It has two banjos (45deg at the caliper, 90deg at the m/c) and goes straight from the caliper to the master cylinder (37.5"), nothing inbetween. See how that works.

The 1in rise and 1in back handlebar riser I had was not really nice, so I had my machinist play around with his machines:

For this season i will try an ignition setting that supports the theory of faster combustion on dual-plugged engines better: 3deg BTDC for static and the full advance at 28deg @ 3200rpm (setting #1 of the OMEGA ignition). See what that does to the gas mileage and carbon build-up.
The sidestand of both, the G/S and the GS is a laugh: skinny and not very comforting. I have asked a fellow Airhead for a loaner of his 1993 R100R sidestand to see whether that can be made to fit a G(/)S. It attaches to the front mounting bolt:

Bingo, that can be made to work, despite the crashbars. The bracket fits to the front motor bolt without changes if no crashbar is mounted. The sidestand itself needs to be extend for the higher G(/)S. I added about 2in I think.
I opted however to have the stand itself custom machined (to make it fit with a crashbar mounted) and made of thickwall stainless. My trusty machinist was doing his magic and a couple of weeks later, this was born and assembled:

It was necessary to extend the shift lever because getting the boot between the sidestand and the shiftlever was too tight. The springs are stock size, but from an aftermarket supplier.

It wasn't cheaper than buying, but I enjoyed being part of the making.

This is the bike after the "re-design" phase in the spring of its second year (and yes, the heavily dented tank was replaced by a less dented tank):

Season 2009 pictures

Now featuring
Adding real horns to the bike:
I found some leftovers in my garage: non-matching design, but matching Hi-Low tones, great sound, they make incredible noise - pointing forward!

Mid-Ohio 2009:
Did a long weekend run to Mid-Ohio as I had never been there before:

Link to Mid-Ohio2009 pictures

Iron Butt SaddleSore 1000
It's called a SaddleSore 1600 for us Canucks (1610km = 1000mls), link to ride report
Winter 2009/2010:
Time to do something about lighting: found a very reasonably priced ($25 + shipping) pair of running lights that have HomeDepot-type halogen bulbs installed, a cheap and cheerful measure to increase visibility, have a better chance to be noticed. Secondly, Klaus Hueneckes Lite Buddies are the ultimate: a cluster of 2 x 4 red LEDs for integration into the indicator housing, shiningg red through the amber indicator glas:

I also bought some Scotch reflective tape to increase visibility of the bike from the side:

Not a Christmas tree yet, but not far from it, eh!

Much better!

Next up: doing something about the increasing oil consumption!
Before I put the engine together in early 2008, I measured the 1977 R100S pistons and barrels: they were barely in spec for both, taper and ovality, even after honing: "The taper on the barrels is more than 0.1mm with only a maximum 0.08mm allowed. Ovality is most certainly more than allowed. The ring end gaps will be just about in spec.". I expected to get no more than 25,000km out of that set.

I made it to about 17k (2 full seasons) when the oil consumption passed 0.7ltr and it was time to re-assess. I have the original barrels of the Nov 1980 built R100CS engine. Only problem is, it has some imperfections in the Nikasil liner. I re-assessed the barrels and decided to use them this time around. What can happen!

Checked prices for piston ring sets at BMW (they are Federal Mogul/Goetze) and wasn't impressed. There are alternatives however: Hastings and Grant. Didn't know about Grant when I started, so I approached Hastings. Their sets were inexpensive but, the oil ring was chromolly which isn't recommend for use with Nikasil barrels, both are hard materials, so chromolly would scratch the Nikasil barrels. So I searched the Hastings catalogs for suitable cast iron rings and this is what I selected for my "C" barrels:

Ring No.BMW stock shapeHastings equivalentNotes
#1Type 032
Barrel Face
3.71" dia.
0.675" width
0.168" wall
part #35896

#1116 cast iron

#2Type 126
Rev Torsional Taper Face
3.71" dia.
0.775" width
0.169" wall
part #29900

#1116 cast iron

#3Type 507
Cast Iron Oil
3.7175" dia.
1.86" width
0.157" wall
part #31635

#1116 cast iron

All six indivdual rings together were less than $50 delivered CONUS. All of them were slightly oversized and I set the end gap to the minimum as per BMW specification: 0.4mm for top and middle ring, 0.25mm for the bottom oil ring. Installed them completely dry in a degreased barrel. For the oil ring to fit, the width and depth of the piston grove had to be slightly increased.
Run-in started with 1min @ 3000rpm and then cool down, followed by 50km hard riding on the road, constantly opening and closing the throttle full in all gears, but mainly first to third gear. Later that day, I went for a leasurely 3hr ride (Nov 8, 18degC). Bike was feeling great, no blue smoke as far as I could tell. Using a normal compression tester, I measured 138PSI compression on both sides with the carbs off on a cold engine. I guess that is as far as it goes before the winter.

After reverting back to the original CR8.2 setup I decided to de-activate the dual-plug option and go single with points-in-beancan, a 3Ohm Dyna dualcoil and a Dyna booster. The plugs are NGK BP7ES.

The second set of plugs and a cheap noname 3Ohm dualcoil now serves as a backup.

I also mounted my new DIY oilsump extension (with integrated oil temperature sensor) ansd sump guard. Both sump/engine and tranny guard are home made.

I always wanted an oil sight glass on the tranny. Bought a standard J.C. Winko fluid sight glass in stainless (part #160FREA/B) and had my machinist change the thread to a M18 x 1.5:

I used a 1981-on RT oil cooler for my conversion. They are easier to come by (especially in Europe) and usually cheaper. A bracket was needed to make it work. The oil filter cover plate (no thermostat) is from a R100GS, so are the oil hoses.

Well, I had a new idea for a gimmick, but in reality, I only wanted to replace the BMW OEM oil pressure switch. I am a visual kinda guy and like mechanical things, so with an analog oil pressure gauge I would be able to eliminate the OEM oil pressure switch. The gauge would show me the health of the oilsupply, if not the engine health. Now, when looking at prices, an automotive 2 1/16" gauge with a reasonable mounting cup sets me back about $100-$120. Not too much for knowing the engine health at all times, but there must be a cheaper way. Also, that gauge requires some space to mount, which, on an unfaired bike, is a luxury. So, one must buy for a total of not even $30:

I used some silicone to waterproof the gauge (I left some areas for venting should the gauge require that). I also fabricated a very small aluminum bracket from some scrap material and JB-welded it to the gauge, together with a "JB Weld"-nut.

Final product:

Note from first actual run on the bike: easily 150PSI on cold engine on higher rpm, that however changes with the engine being warmed up properly to 20PSI at idle, 60+PSI @ 4000+rpm, all working well despite my first doubt.

Season 2010 pictures with early G/S Paris Dakar tank

I weighed it in dry (incl all oils) at 206kg/454lbs (w/ empty 32l tank).
I thought I was more around the 205Kg/451lbs mark like the original 1981-1987 G/S Paris-Dakar with full tank, but the optional accessoires such as the luggage carrier, crashbars, 2 bashplates, tool roll plus additional tools, oilcooler, starter, Corbin seat, R100R exhaust etc as well as the 1988-on GS forks do account for significant add-on weight compared to the G/S Paris-Dakar.
Latest gadget addition to keep dirt and water away from the rear shock piston:

Ohlins "leg warmer" made by and thanks to ADVrider inmate corrado113.

My fuel consumption so far has been bad, 7.3l for 100km (needle 3rd from top). I went in and changed the needle back to stock (40mm Bing), which is 2nd from top. The consumption immediately went down to 6.2l per 100km (37mpg) on a 1500km mixed ride (mostly tarmac/gravel at around 100km/h). That gives me a operating range of 515km, without margin.
In a further attempt to lean the bike out for better mileage (rather than peak performance) I changed the needle position to the 1st notch and switched the main jet to 155: no hesitation, stumble or pinking. The sparkplugs after 4min at 4000rpm look like this, white isolator, two-colored electrode and black, but not sotty rim -> nearly perfect:

End of the season 2010:

Maintenance Log and Gas Mileage


Left cylinder:

Right cylinder: