00 BMW 1977 R100RS Update after 4,400 Miles

Prior to riding the bike [which I named “Gonzo” as I tend to name my bikes after muppet characters 🙂 ] to Pennsylvania for a rally celebrating the 40th anniversary of the introduction of the R100RS into the US, I rode the bike for almost 1,000 miles to sort out any issues that arose.

Gonzo with Starting Mileage The Morning I Left for Pennsylvania

Gonzo with Starting Mileage The Morning I Left for Pennsylvania

Every build I have completed requires me to address a number of problems until the bike is stable. Despite the nearly 1,000 mile shake down, I had a transmission problem on the trip that required removal, disassembly and putting the transmission back in the bike. I show why the problem occurred below.

The work was done by Tom Cutter at Rubber Chicken Racing Garage who fortunatley attended the rally and lives about an hour away.

In two months, I have ridden Gonzo about 4,400 miles and decided to document what issues, changes and corrections I made over that time.

I sometimes get comments from people who read my documentation that think I must be an airhead guru. Nothing could be further from the truth as this list of mistakes I made when building Gonzo shows. However, with some perseverance, and help from the real guru’s, I can correct the mistakes and eventually my builds become reliable.

First Engine Start Status

The engine started for the first time without any difficulty, but did require the choke to get going. Here is what I corrected.

  • It ran a bit rough toward the end of the 60 second run at 3500 – 4000 RPM. I managed to unscrew the nipple that secures the cable to the choke housing. This prevented kept the choke on after I closed the choke lever.
  • The generator light flickered. I found this is a known condition of the Katdash flexible circuit board LED lights. The LED can respond to the voltage regulator cycling on/off if there is no load on the alternator. The fix is to turn the headlight on to create some load.
  • The front brake felt soft. I removed the master cylinder hose clamp, put a piece of wood under the rear of the cylinder so the brake light switch was down hill from the brake fluid reservoir and pulled the brake lever tight at the handlebar with a bungee cord over night. It’s easy for a small air bubble to lodge in the orifice of the front brake light switch as it is down hill from the reservoir.

First Ride Status

The first ride was about 5 miles and enough to warm the engine sufficiently to balance the carburetors.

  • Front engine mounts were loose
  • The repair to the right lower fairing panel included a new brass insert. The threads were not clean so I chased them with a tap so the M6 bolt would thread easily.
  • The front brake pads were not touching the rotors evenly so I adjusted the caliper eccentric pins.
  • After the ride, I used my Grok carburetor balance box to get the carburetors synchronnized.
  • Clock face rotates. I had it rebuilt but the clock face was loose inside the housing. I sent it back to Terry Vrla and he quickly corrected the problem and returned it.

First 30 Miles Status

I rode the bike for 30 miles and then changed all the fluids. In particular, I want to get rid of the engine assembly lube and also look at the oil filter paper for signs of something bad happening in the engine.

  • The left fork was leaking fluid at the bottom. I tightened the drain bolt assuming that was the cause.
  • The swing arm boot was leaking gear oil. I positioned the rear strap and tightened it. It was on the curve of the housing instead of the flat part.
  • Install the repaired clock.
  • Add thread protectors to fairing screws.
  • Adjust handlebars raising them 1 inch using ACE hardware spacers. At the stock height, I could not rotate the levers to a comfortable angle as the cable adjusters contact the edge of the top triple plate. The added 1 inch improved my riding position and provided enough clearance so I could rotate the levers down enough that I can reach straight out with my fingers to grab them instead if angling my fingers upward which stresses the wrists and strains the carpel tunnel tendons.
  • Change oil, filter and gear lube. The filter showed small bits of material: some shiny aluminum bits, a small amount of steel bits and a speck or two of rubber. Nothing major. The transmission drain plug had collected a paste of metal, but no sharp bits at all, so nothing to be worried about.
  • I torqued the head bolts and reset the valves. The head bolts had loosened a bit which is expected.
  • I lost several fairing screws. The stainless steel ones I used don’t seem to tighten completely in the clip. I ordered a number of screws and clips from BMW.

200 Mile Status

At 200 miles, there were a number of issues and things to change.

  • The top fairing side panel and top headlight panel were secured to the top faring bracket with wood screws similar to the ones used on the top front headlight panel. I was too ignorant to know these are the wrong fasteners when I put the fairing back together. The wood screws would not hold and backed out. I learned the top headlight panel has threaded inserts for an M6 bolt. As I replaced the top headlight panel with a used due to extensive damage to the original, I now had the brass M6 threaded inserts in the top front headlight panel and that’s why the wood screws wouldn’t hold. I pull the top panels off to see if I damaged the threads in the inserts, and found I hadn’t. I reassembled the faring using the M6 screws.
  • I checked the valves. The left exhaust had moved from 0.008″ to 0.006″ while the right intake had moved from 0.004″ to 0.006″. When I torqued the head bolts the left was a bit loose. I reset the valves.
  • I adjusted the foot shift linkage as I wasn’t able to down shift without bumping the edge of the lower fairing panel.
  • There is an oil leak at the bottom of the front engine cover. There was oil coming out of the hole for the lower bolt. It had a heli-coil insert and I figure it was drilled too deep and cracked the back of the inner timing cover. I used grey RTV to fill the bottom of the hole.
  • The left mirror rattles against the faring. I cut out a rubber gasket to fit between the mirror bracket and fairing on the outside and a second one that goes between the studs and the top fairing bracket gusset. It improved this but didn’t eliminate the rattle at 2000 – 2500 RPM.
  • I repaired the right lower fairing panel and installed a new threaded insert before having the panels painted. My repair failed. So I removed the panel and made a new boss with a new brass insert with Plast-aid. I inserted a washer over the base of the plastic bushing the inserts goes in to reinforce it. I stacked several washers on top to form a column and poured the Plasti-aid into the hole in the stack of washers and let it set up. So far, this repair is holding.
Washer Stack To Cast New Lower Fairing Boss

Washer Stack To Cast New Lower Fairing Boss

Plast-aid with New Brass Bushing Setting Up To Form New Lower Fairing Boss

Plast-aid with New Brass Bushing Setting Up To Form New Lower Fairing Boss

    • The alternator “Y” terminal was loose so I removed the stator cover, tightened it and reinstalled the cover.
    • I added shrink tube to the three phase wires that connect at the alternator. But the  shrink tube on the “red” phase wire wasn’t covering the spade on the back side, so I replaced the shrink tube.
    • I still have a leak on the left fork at that bottom. I torqued the large nut at the bottom to 77 FT-Lbs. It stopped the leak.
    • The foot  tab on the center stand had broken and I had a piece welded to the stand. But it was too low and dragged in the corners. I bent the end of it up so the foot pegs would be the first to touch.
    • I checked the pan bolt torque. They were a loose and I set them to 72 IN-Lbs. The pan gasket compresses after a few miles so this was expected.
    • I added an air deflector to the Clear View wind screen to adjust the height of the free air flow to reduce noise.
Wind Deflector Installed

Wind Deflector Installed

  • I installed a mount on the handlebar for my GPS.
  • The rubber gasket at the bottom of the windscreen contracted leaving a gap. I loosened the bolts and tried to stretch it out and broke it. I ordered another gasket.
  • There still is an oil leak from either the front engine cover or the oil pan gasket
  • I checked the pan bolt torque. They were a loose and I set them to 72 IN-Lbs. The pan gasket compresses after a few miles so this was expected.
  • The cam shaft seal is not leaking. I’ll keep an eye on this and see if I can identify the source of the oil leak.

750 Mile Status

BMW had a 600 mile service for new bikes and I went over the bike at this point. I changed the oil and gear lube one more time looking for any signs of problems.

  • Change engine oil, filter and gear lube. When I removed the filter paper, there we no flecks of metal or bits of rubber on the paper. This is a good sign.
  • The transmission drain plug had fuzz but nothing is sharp, just a very smooth paste.
  • The tank does not have rubber knee covers as were used on the large tank for the /5 bikes. I can see some scuffing from my Aerostitch suit. I ordered some protective film for the tank from The Tankslapper and install it.
  • I install the new windscreen rubber gasket. I loosen all the bolts and carefully insert the seal between the bottom of the screen and the fairing. I have about 1 inch of the seal extending past the rear of the windscreen on both sides. Then I trimmed it with about 1/4 inch still extending.
  • I bought a pair of “Kathy’s Journey Designs” bags that fit between the fairing and the gas tank and sit on top of the lower fairing bracket to add some storage space when I’m touring. I put a piece of 3-1/2 x 11 inch foam board in the bottom to help expand them and keep them level when mounted. My air compressor fits nicely in one of them.
Wolfman Tank Bag with Kathy's Journey's Fairing Bag

Wolfman Tank Bag with Kathy’s Journey’s Fairing Bag

  • I got another set of straps for my Wolfman tank bag so I can mount it on the gas tank.
  • I checked the timing and it had not changed.
  • Tire pressure was holding at 33 PSI front and 36 PSI rear.
  • I installed a set of Hebco-Becker panniers I had for touring.
  • I tweaked the foot shifter linkage to improve my foot position. Now I don’t seem to bump the lower fairing panel with my foot when down shifting now.
  • I still have an oil leak around the front of the engine somewhere. I pulled the alternator and can see oil leaking from the front crankshaft seal. I replaced that, so why it’s leaking wasn’t immediately clear.  And then, I figure out what I did. I had to heat the inner timing cover after I installed it to be sure the crank nose bearing was fully seated. I used my MAPP gas torch which has a wide flame. I fryed the seal :-(.  I should have used my propane torch with narrow tip to keep the flame away from the seal. I order a new seal, but it’s close to when I leave for Pennsylvania, so I hope it arrives in time to install it.

960 Mile Status

  • I added a sunshade to the GPS to shade the screen. The angle I have to mount it to clear the fairing tilts it toward the sky and increases glare.
  • I install the new front crankshaft seal and do a test ride of about 10 miles.  So far, no oil at the bottom of the front engine cover.
  • I wash and wax the bike.

4,400 Mile Status

At the 960 mile point, I loaded up the bike and rode it to the 40th R100RS anniversary rally in eastern Pennsylvania hosted by Todd Trumbore. I documented the trip and my adventures here:

I used about 3/4 quart of oil in 1,500 miles on the way out. But on the 1,850 mile ride back to Denver, oil consumption dropped to less than 1/4 quart. The rings seem to have seated in.

The cam roller circlip came loose and the roller cam came off requiring me to trailer the bike the final 350 miles to the rally. Here is a picture that explains why this happened.

My Incorrect Size Circlip (Left), Correct New One (Right)

My Incorrect Size Circlip (Left), Correct New One (Right)

The new circlip I purchased from my dealer is not the correct size. I was not attentive enough and also failed to compare it to the old one to sanity check that the new one was correct. So, the lesson for all of us is “check your parts” because human beings work at BMW and they are capable of making unintentional mistakes, just like we do. 🙂

There are not many parts counter folks who really know airhead parts well enough to catch a mistake like that, particularly when a dealer has to order the parts from BMW which is the typical case for airhead parts. In that case the parts arrive in a sealed bag specifically for you. Most parts folks will call you to pick up the parts and are not going to verify what they received from BMW is what you ordered for two reasons; they likely don’t know airhead parts well enough to make that determination, and they don’t have the time.

As another example of unintentional parts mistakes, I ordered the upper and lower rear brake shoes and I received two brake shoes each in a bag with the correct part numbers. But the top shoe bag had a lower shoe in it and I didn’t notice that until it was time to install them. No great harm, but its another example of why checking what you receive when you receive it at the parts counter is a really good idea.

At times like this, I take a deep breath and recite Confucius’ “By Three Methods Do We Gain Wisdom”:

“By three methods we may learn wisdom:
First, by reflection, which is noblest;
Second, by imitation, which is easiest;
and third by experience, which is the bitterest.”

I usually seem to end up learning by the third option 🙂

Tom Cutter of Rubber Chicken Racing Garage fame attended the rally and at the end he put my bike on his trailer and I rode his R100 “Fake S” to his house. He removed, disassembled, cleaned, assembled and reinstalled the transmission for me. Along the way, he noted several corrections I need to make. I only ended up adding one day to my return trip to Colorado. It’s impressive to watch someone with 45 years experience do what I have only done once. The precision and smoothness of the work flow is an exemplar for me for my future projects.

  • Right carburetor throttle plate is not centered correctly which makes it hard to adjust the idle.
  • Many fasteners seem loose. That’s interesting as I torqued most of them. They are stainless steel with anti-seize so I’m curious if they loosen up by themselves.
  • The clutch action is not crisp. Cause unknown but could be the cable.
  • I installed the rear brake cam backwards which Tom corrected.
  • I have a /6 and /7 throttle cable installed (9 mm lock nut and 10 mm lock nut).
  • My volt meter will suddenly start swinging back and forth, on occasion violently. I cleaned all the connections, but I will pull all the meter wires and the alternator wires and verify they are tight. I have a crack in the brush holder that I tried to repair and a crack in the metal housing around the stator so I will replace the holder and housing.

So, I have some projects to work on now that I’m back home in Colorado.

9 thoughts on “00 BMW 1977 R100RS Update after 4,400 Miles

  1. Thanks, Brook! You demonstrate the value of good preparation, a healthy body of knowledge and willingness to ask for support when needed…a great model for those of us contemplating a journey like yours.

    What was the issue with your transmission and did Tom pull it, repair it and reinstall in one day? You make it sound like a pit stop during a race!

    Cheers, Peter

    • Hi Peter,

      To your question, the second link in the 4,400 Mile Status section will explain the resolution to the transmission circlip problem. Tom completed the work in a little over eight hours including correcting a couple of mistakes I made elsewhere. Yes, what would take me many times longer, he did in a trice.

      Brook Reams.

  2. Interesting to read about the bugs and testimony to the need to be patient and pay attention to the details. Good admonition!

  3. Brook, maybe you should have gotten the extended warranty!
    Your documentation of problems to fix makes me think I should avoid restoring an Airhead. Thanks so much for sharing.

    • Michael,

      Yeah, one of the voices in my head said I should get the extended warranty the other said it’s not worth it and the third told them both to shut up, I need to concentrate 🙂


  4. Just finishing off the refurbishment of my 1977 R100RS with much assistance from your articles! I hence decided against touching the gearbox especially as the bike ‘only’ had 59000 miles. In fact I have left as much of the engine alone as possible

    The push rod oil seals now leak – there is no escape the affects of age on rubber -so I have had to lift the barrels but in doing so I notice no visible wear on the cylinder bores.

    So It raises the question at what mileage should one take the engine apart in doing a BM refurb’, and dare I mention it, the gearbox!

    • Hi Stuart,

      I suppose if you aren’t experiencing any problems, then the adage of “Let sleeping dogs lie.” applies.

      That said, there are known issues with the valves in the 1970’s-mid-1980’s airheads caused by no-lead fuel and BMW’s changes in valve & seat metallurgy as they looked for the right materials to survive without the lead lubrication of the valve face and seat. Valve clearance that closes up in 5,000-7,500 miles is the early indication you need the heads rebuilt.

      Gearbox noise lets you know bearings are going. When that happens, sooner is better than later to have it rebuilt by a professional.

      I hope that helps.


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