BMW K100 8 Valve Motorcycle – Last revised: March 20th, 2025
Maintenance, Parts Reference for Alternatives / Substitutions, Tips & Tricks, and Funky Hacks
Welcome to my collection of information about my 1985 BMW K100RS, manufactured July 1984 in Berlin, Germany.
Yes, communication is easy using the contact form. One may notice a bit of typing dyslexia on this site.

Vehicle originally sold in Ft. Worth, Texas and I purchased in Austin, Texas in 1998 with 13,400 miles on the odometer. Bike had not been running for a few years and a major upgrade from my 1970 R75/5 and 1976 R90/6. Aals it had low speed drops on both sides, hence the $1,500 price tag.
Current Odometer Reading: 133,000 miles (214,000 kilometers)
Expected Repairs:
- driveshaft u-joint & throttle cable- original (133 mi. @ 41 years old)
- water/oil pump seals (26k mi. @ 17 y.o.)
- thermostat (60k mi. @ 24yo.)
- coolant temperature sensor (71k mi. @ 25y.o.)
Component Failure/Replacement Intervals
So you want to buy, ride, and operate a classic BMW K100 8 Valve Motorcycle?
Brakes
- Brake Calipers (rebuilt) 63k @ 15yo. | 67k @ 25yo.
- Brake Rotors – 130.5 mi. @ 37yo. (EBC)
- Brake Pads – 63k mi. @ 15 yo. | 48k mi. 16yo. | 30.5k @ 16yo.
- Front Brake master Cylinder – 55k mi. @ 15yo. |
- Rear Brake Master Cylinder – 55k mi. @ 15yo. | 81.5k mi @ 24yo. (Chicom)
- Rear Brake Switch – 130.5 mi. @ 37yo. (Magura)
Chassis
- Fork Seal (R) – 84.2k @ 29yo. | (R) 17.8k mi. @ 5yo.
- Rear Shock – 62k mi. @ 15yo. | 60k @ 16yo.
- Steering Head Bearings – 54.5 k mi. @ 15yo.
- Swing arm bearings – 66kmi. @ 16yo.
- Wheel Bearings – 64.4k mi. @ 15yo.
Cooling
- Radiator Cap- 132.75k @ 40yo.
- Radiator Fan – 89.1k @ 20yo.
- Thermostat – 72k mi. @ 16yo.
- Water Pump – 86k mi. @ 30yo.
Drivetrain
- Clutch Cable – 8k mi. @ 13 yo.
- Clutch Plate – 49.5k @ 14yo.
- Transmission 2nd Gear – 49.5k @ 14yo.
- Transmission Shift Drum 49.5k @ 14yo.
Electrical
- Alternator Bearings – 131.6k mi. @ 39yo.
- Alternator Brushes – 126k mi. 31yo.
- Ignition lock – 63k mi @ 15yo. (rebuilt)
- Monkey Nuts – 130.5 mi. @ 37yo.
- Starter Motor – brushes, o-rings, oil seal 124k mi. @ 31yo.
- Voltage Regulator – 126k mi. 31yo.
Engine
- Engine Oil Pan – 89.1k @ 30yo. (reseal w/ RTV)
- Exhaust Valve -76k mi. @ 18yo. (#4 cyl. cracked, replaced all 4)
- Oil Sight Glass – 55k @ 15yo. | 73k mi. @ 16yo.
- Rear Main Oil Seal – 49.5k @ 14yo | 81.2k mi. @ 19yo.
- Valve Cover Gaskets & Bolt Grommets 94k mi. @ 20yo. | 36.6k mi. @ 17yo.
- Z-hose – 69k @ 16yo. | 55k mi. @ 15yo.
Fuel Delivery
- Intake Rubber Bellows – 76k mi. @ 18yo.
- Fuel Cap 55k @ 15yo. (upgrade)
- Fuel Cap Gaskets – 155k @ 15yo. | 30.5 mi. @ 37yo.
- Fuel Line; internal – 55k @ 15 yo. | 111k mi. @ 7yo.
- Fuel Pressure Reg. 69k mi. @16yo. | 12k mi. @4yo. | 49k @ 2yo. | 2.25k @ 3yo.
- Fuel Pump – 69k mi. @ 15yo.
- Fuel Pump Rubber Dampener – 55k yo. @ 15yo.
- Fuel Cap – 55k mi. @ 15yo.
Ignition
- Coolant Temperature Switch – 62k @ 15yo. (replaced w/ BMW part)
- Hall Effect Transmitter – 76k mi. @ 18yo. | 56.5k mi. @ 21yo. (Endurolast)
- Ignition Coils – 130.5 mi @ 40yo. (Endurlast)
- Ignition Lock – 63k mi. @ 15yo.
- Spark Plug Wires – 77k mi. 18yo.
Drivetrain
- Clutch Cable – 8k mi. @ 13 yo.
- Clutch Plate – 49.5k @ 14yo.
- Transmission 2nd Gear – 49.5k @ 14yo.
- Transmission Shift Drum 49.5k @ 14yo.
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Maintenance
– BMW K100 8 Valve Motorcycle –
Parts | Tips & Tricks | Funky Hacks | Hyperlinks
Download a 180Mb+ zip file containing my current collection of repair manuals, diagrams, & service bulletins. All of this easily loads onto my 7 inch Android 4.1 tablet I have giving easy access in a compact sytem stored in y topcase. A Butt load of information. (Yes, that about two hogsheads worth!)
My choice for fluids & lubricants based on three criteria: quality, price, & availability. One may disagree so take a quick look at the products I use. The more I learn, the more I upgrade. It my be a shock that overall I use a main chainstore brands products getting maximum value and top notch quality.
Quick PDF download of BMW Motorrad’s required maintenance. This what the dealership use. Personally I just keep a text file lisitng past and presents repairs. This allows extremely easy search function when researching last repair or modification.
Complete list of scheduled and unexpected repairs. Over 25 years of records. Goal is to analyze data into simple statisitcs, i.e. Actual oil change interval, how long did the fuel pump last, et al.
For example: Oil changes on average every 2k miles / 6 months. Seems excessive but since moving North driving less miles over time.
Fluids & Lubricants
– BMW K100 8 Valve Motorcycle –
Item Specifications (BMW Rider Manual) | 1st Choice | 2nd Choice |
---|---|---|
Motor Oil Brand-name HD oil for 4-stroke egines; API classifications SE and SF. 4 qts. / 3.75 liters | Super Tech Full Synthetic Heavy Duty SAE 15W40 – $15.84 gallon as of March 4th, 2025 – High ZDDP levels – Full Syhthetic – High Detergent – Available Nationwide – API CK-4/SN, CJ-4, CI-4, CI-4 Plus – Oil analysis (view) | PENN GRADE 1 Synthetic Blend SAE 15W-40 – $34.33 gallon (case price 12 qts.) as of March 4th, 2025 – High ZDDP levels – High Performance – No API Rating – Order Online – Manufacturer speifications (view) |
Gear Oil SAE 80W90 Gearbox 850cc Rear-wheel drive 260cc | Super Tech Full Synthetic Gear Lubricant SAE 75W-90 – $10.43 quart as of March 4th, 2025 | Valvoline SynPower SAE 75W-90 Full Synthetic – $16.93 quart as of March 4th, 2025 |
Telescopic Fork Oil SAE 5 / 360cc per fork leg | Valvoline Dexron VI/Mercon LV Full Synthetic – $6.83 quart as of March 4th, 2025 – SAE 6 | Bel-Ray 5W High Performance – $17.38 quart as of March 4th, 2025 – SAE 5 |
Engine Coolant 2.9 qts. / 2.8 li. ( I use 40% coolant / 60% water using this chart. To do this I add 0.5li. of distilled water to the empty system, then fill with the prediluted coolant.) | Super Tech 50/50 Prediluted Extended Life for BMW – $11.83 gal. as of March 5th, 2025 – OEM stabilized silicate enhanced organic acid – Extended life up to 5 years or 150, 000 miles – Prediluted 50/50 for easy use – Designed for European vehicles (BMW) | BMW Antifreeze/coolan – $35.00 gal. as of March 5th, 2025 – Part # 82141467704 – Concentrated Dilution Required – Contains no nitrates or phosphates – Bittering Agent Added |
Brake Fluid DOT 4 | Super Tech DOT 4 – $3.93 12oz. | BMW 81220142156 DOT 4 -10.99 12oz. |
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Parts Reference for Alternatives / Substitutions
– BMW K100 8 Valve Motorcycle –
Maintenance | Tips & Tricks | Funky Hacks | Hyperlinks
Alternatives / Substitutions based on items I have used / replaced and current ease of availabilty not megalists.
Stock | Currently Using | Alternate / Substiutions / Notes |
---|---|---|
Air Filter BMW 13721460337 ~$50.22 | EnDuraLast AF-337 $25.99 as of March 5th,2925 | MAHLE LX 75 $47.78 as of March 5th, 2025 |
Alternator Bearing; Front | SKF 6203 2RS – 40x17x12mm | Amazon | EBay |
Alternator Bearing; Rear | SKF 63001 2RS – 28x12x12 | Amazon | EBay |
Battery BMW 61211459650 ~$178.94 | SigmasTek SP12-22HR Replacement Battery – 12 Volt $46.49 as of March 6th, 2025 | Best alternate ever, matched with a C-TEK AGM battery charger and the battery dependabilty has been great. |
Brake Pads (2 Sets) BMW ~$134.90 | Sixity Organic Brake Pads FA18 (2 Sets) $19.22 as of March 10th, 2025 | EBC FA18 Kevlar Organic Front Brake Pads (2 Sets) $36.15 as of March 10th, 2025 |
Coolant Temperature Sensor BMW 61311459197 ~$63.03 | Vemo V40-72-032B (German brand) $26.31 as of March 6th, 2025 (EBay) | |
Crush Washers; Metric | Glarks 470-Pieces Aluminum Metric Size M6 – M24 | Great money saver. |
Fuel Filter | Purolator F60146 | WIX 33032 / NAPA 3032 |
Fuel Injectors BMW 13641460450 | EnDuraLast FInj450EDL $56.50 as of March 10th, 2025 | BOSCH 0280 150 210 BORG/WARNER: 57076 |
Fuel Line (external) | Gates 27340 (price per foot) $3.94 as of March 13th, 2025 | SAE 30R14 T2 |
Fuel Line (in tank) | Gates 27093 (price per foot) $33.78 as of March 19th, 2025 | Submersible SAE30R10 100PSI |
Fuel Pressure Regulator BMW 13531460451 ~$289.29 | Herko PR134 $28.00 as of March 10th, 2025 (EBay) | Beck/Arnley: 158-0073 Bosch: 0280160200 |
Hall Effect Sensor BMW 12111459033 ~$871.00 | EnDuraLast BOIgnSen-K033EDL $185.00 as of March 10th, 2025 | 2AV54 and CYHME56 Rebuild |
Oil Filter BMW 11421460845 ~$24.52 | Purolator PL10241 $9.84 as of March 5th, 2025 Fun Fact: Purolator invented the oil filter. | Previously used: AC PF53 – $7.74 as March 5th, 2025 SUPERTECH ST3614 – $3.84 as March 5th, 2025 |
O-ring; oil filter cover (88x 3 mm) BMW 11131460425 ~$5.24 | Nitrile (buying pack of 25) $0.80 ea. as of March 14th, 2025 | Viton (buying a pack of 5) $4.60 as of March 14th, 2025 |
O-ring; clutch nut (19 x 4 mm) BMW 11211460467 ~$2.74 | Viton® (buying a pack of 10) $1.70 ea. as of March 14th, 2025 | Difficult to access so definitely upgrade to Viton. |
Radiator Thermostat BMW 17111460716 ~$89.61 | BMW – 24 yo. & 72k mi. Previous failed at 16 yo. & 61k mi. | EnDuraLast Thermostat716EDL $39.99 as of March 6th, 2025 |
Spark Plugs (non-resistor) Bosch X5DC BMW 12129062217 ~$9.40 Voltage Regulator BMW 12311459286 ~$137.57 | NGK D7EA or 7912 Set of 4 – $20.95 as of March 4th, 2025 Beru AG 0190005001 14.1 volt | NOTE: Cross reference charts are a good start but one must then check the manufacturers information to insure non-resistor plugs. Don’t ask me how I know… EnDuraLast $36.00 as of March 10th, 2025 |
Wave Washers | 300 Pcs 7-Size Metric 304 Stainless Steel $11.99 as March 10th, 2025 | Great money saver. |
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Tips & Tricks
– BMW K100 8 Valve Motorcycle –
Maintenance | Parts | Funky Hacks | Hyperlinks
A collection of information a lot of folks know about but some sure could use.

ANDROID APPS
A few unique applications one may not be aware of.
APK | DOWNLOAD | NOTES |
---|---|---|
BMW Motorrad Parts | https://bmw-motorrad-parts.en.uptodown.com/android | Don’t leave home without it! If you don’t have a computer in your repair shop, this will have to do. |
DigiHUD Speedometer | https://digihud.en.uptodown.com/android | No longer on Google Playstore. This simple efficient app uses a phone’s GPS instead of data. Color adjustable with an uncluttered display, it even has a compass direction setting. Newer apps put so much info visible it seems distracting, So KISS, Keep It Simple Stupid, and one will discover with 3G coveration gone in the USA, Android phones are cheaper than eggs. Very accurate and easy to view, see for your self. (or maybe not, picture cooming soon enough) |
Physics Toolbox Sensor Suite | https://play.google.com/store/search?q=physics%20toolbox&c=apps | Total nerd application for the junior scentist in your innerself that’s just waiting to be explored. Geek out! |
wX | https://play.google.com/store/search?q=WX&c=apps&hl=en-US | It took years of trying to find a simple and ad free weather app. This is clutter free and direct- everything you’ll need on an adventure (or daily use). |
Bliss Operating System | https://docs.blissos.org/knowledgebase/other-bliss-variant/surface-builds/ | Do you have an old Miscrosft Surface device and love the conveience and apps for Android? Now you can have all those apps at your finger tip with the BlissOS for Surface devices. The speed of a i5 processor, large hard disk, and 4GB on my Surface Pro make it a great travel companion and repair shop addition. Escape that small screen and maximize productivity with a larger screen. |

CHEMICALS – Absolute Must Haves for Optimal Maintenance
PRODUCT | USE | NOTES |
---|---|---|
LIQUI MOLY LM 508 | Anti-Seize Compound | Take 20% off torqe wrench settings when using. |
Brake Cleaner | Cleaning metal surfaces | Always buy 2 cans, fastest and easiest way to get ‘er done. |
Contact Cleaner | Cleaning electrical contacts | A squirt of this then some Deoxit and your connections will be it electron heaven. Great Automotive MAT sensors. Good alternate is white vinegar for corrosion. |
WD-40 All-Purpose Lubricant | Metal cleaner | Water Dispersant created on the 40th attempt I never use as a lubricant. Use on alloy engine covers w/ a toothbrush for a nice clean finish. Use homemade DIY Engine Degeaser after WD-40 leaves a residue that attracts dirt and grime. |
DeoxIT D100L-25C | Electrical connnection cleaner and enhancer | One of the best products ever. works well. Seems expensive but bottle lasts years. |
Volkswagen Fuel Additive 90ml | Valve Cleaner | After seeing dozens of videos and reading forums, my selection for removing valve stem deposits. A few drops on a dirty sparkplug tilted upside will, after a soaking awhile, really clean them well. |
SeaFoam Motor Treatment | Combustion Chamber Cleaner & Fuel System Cleaner | Once again, After seeing dozens of videos …. Use in a tankful before your engine oil change. |
BW-100 Freeze Spray | Changing Rear Brake Rotor | Using a butane torch heat the bolts then zap them with freeze. Using an impact driver and a solid whack with a hammer and voila!, out they come. |
Y’allCanDiy 2 pack | Medium/High Strength Thread Locker – great alternative to LocTite | Wow, a two pack of blue and red Anaerobic Locktight at 1.69oz. each. Fabulous value, you’ll never rum out! |
Liqui Moly Pro-Line 2037 | Engine Flush | I am no longer able to ride the snot out of my bike due to Ohio’s short riding season and career as my mother’s caregiver keeps me close to home. Plenty of engine flushes to choose from but this one worked best for sticking starter sprag. |
Dielectric Silicone Grease | Dielectric & rubber preservative | It’s like hot sauce – one will put it on everything (rubber) to protect and stop dry rot. (Exclude tires) |
Engine Degreaser | DIY | 1 part ammonia, 1 part liquid laundry detergent, 1 part white vinegar – add a to a spray bottle. Amazing! |
Wax Stripper | DIY | Gently mix: 1 cup liquid dish soap, 1 cup baby shampoo, 1 cup water, 1/4 cup white vinegar, 1/4 cup baking soda Then add 1 gallon of water and sponge wash painted surface. Works amazingly! |
Penetrating Fluid | DIY | 50/50 blend of ATF & acetone works well and is economical. I use an old “3-in-1” oil can for easy application and reduced spillage. |
TOOLS
Homemade & Essential making maintenace easy peasy lemon squeezy.

Battery Charger TEK (56-958) MUS 4.3 POLAR
Who in their right mind would pay ~$130.00 for one? I did and one of the best devices I have ever owned. Used on my Chevrolet Cruze also and its battery lasted 8.5 years. Soldering an extension to the 12 volt lead and it reaches all around my garage. How could I justify purchasing such an expensive unit? I waited until it was on sale and Amazon offered me $60.00 to apply for a credit card. My final price was ~$40.00 and after 5 years has held up remarkably. As of March 11th, 2025 the device is on sale so one may grab the saem great deal I did. Oddly, this looks identical to a BMW charger priced at $222.00

So many to choouse from and mirror on the wall says it’s the luxurious tool of them all. I opted for a cordless model as it is easiy to travel with (and get in tight spots). My game has been upped and super funky hacks taken to the next level.

Manometer for Throtlebody Synchromization
I tried using the “long hose” method which was a simple design but the fluid seem to move to fast. Using glass jars, rubber stoppers, and 15W-40 motor oil made it less of a panic as the fluid moved slower. Do a sync at every sparkplug change. Mileage optimization and silky smooth off-idle throttle response is within your grasp.

Brake Fluid Exractor (DIY)

One can’t be considered a decent mechanic without a torque wrench. Alas the true sign of an exprienced grease monkey is the collection of hammers. A dead blow hammer is the perfect tool for those important taps one has to be accurate on the first attempt. Not having any rebound is just as important. I don’t have an air/electric impact wrench driver but this gets close enough to be invaluable.

Pop! And those pesky fuel are off- often used in unexpected and alternate odd situations. I travel with these on long journeys.

Luckily found on Ebay for under $10, I haven’t seen another one like it. Great for those low torque crtical items such as the fork oil drain plugs and oil filer cover bolts.

Taking the specifications for the BMW tool and using a cheap Chicom grinder on Chicom seal puller to make a usable device. Sure the metal is cheap but since I use it every 60k miles it is good enough. A pick and magnetic pickup tool, along with a spreadsheet, do the trick. (video). I do it w/o the locking tool and just depressing the bucket w/ the tool- it’s a new skill indeed.

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Funky Hacks
– BMW K100 8 Valve Motorcycle –
Maintenance | Parts | Tips & Tricks | Hyperlinks
Super Custom Home Brew Knucklehead Engineering
- 12 Volt Power Outlets – Odd Pair
- Auxillary Dashboard Mount
- ESK Valve Cover Protectors
- H4 Xenon Depot Xtreme LED
- Heated Grips
- Ignition Coils – Finding Unobtanium
- LED brake light
- Panniers; Repairs & What’s Inside
- Power Tap Locations
- Quick Panel Removal
- Relays
- Seat Lock & Practical Helmet Lock
- Side Mirrors – retain & dampen
- Topcase; Fastening & What’s Inside
- Vacuum Port Block Setup Kits
- Windscreen Decor & More
- Upgrades using doughnuts
12 Volt Power Outlets – Odd Pair
If one has a dual 12 volt socket outlet on top the coild cover, why not convert one to a standard automotive size? It will cost half of an adpater or Euro-plug to be able to use it. Obiviously most 12 volt acessory devices come with this larger size anyways.

Need a place to mount an adroid phone as a digital speddomtere, GPS, & a garage door openeer? Look inside the green box and one can see a piece of Zinc-Plated Steel Perforated-Round Angle metal bar attached. Using the bolts that adjust the windscreen flap attaches securely. Of course it’ll take a bit of Slavic engineering but having certain items in plain view and reach is a big plus in my book (or my bike’s webpage).



I am not a big fan of crash bars so I opted for these on both sides of my engine. No longer available at EuroMotoElectric in the States, KpartsHolland still offers them. Having the misfortune back in 1998 of sliding out on a turn at night on diesel fuel in the pouring rain in Bavaria, I can only request everyone remembers to install the fuel caps after a fill up. One broken finger, a hole in my left valve cover, and a bunch of adrenline were the consequences. To return to my campsite, I stuffed a bandana in the hole and drove until the oil pressure light came on. Once it lit, I pulled in the clutch, killed the engine, and coasted. Bike almost to a stopped, I retstarted it got up to speed until the oil pressure warning light flashed, then repeated the process. Luckily being in Munich the valve cover was only US$65.00 (now there over $200 in the USA). May I recommend getting a pair before the become unobtanium.

Check Sparksmith for specifications. My decision based on the folding heatsink fins as opposed to having a fan (or a super cheap Chicomm bulb). No tmuch clearance for a fan. Sold as single units instead of an automotive pair, I carry a regular Halogen as a back up incase the buld or driver fails. Good light pattern in a square K headlamp and extremely visible light improvement. 25 watts of power used which is half that of standard halogen H4. Legal in the USA? Times are changing…
One can view a YouTube video showing more details.


Port Vacuum Block Intake Manifold Kit
Easy to do with nylon tees but for the price and durability of this set up I went for it. So goodbye to rotted and missing vacuum caps. The 5/16′ vacuum hoses did no fit on the throttle body port nipples tight, so I put shrink tubing the exact size of the hose but did not heat it. Before slipping the shrink tubing over I strecthed it a smidgeon with needle nose pliers. Once slipped on the port nipples it was a snug and secure fit.


Coming soon…
Power Tap Unused Fuse Locations
Relays
Ignition Coils – Finding Unobtanium
LED brake light
Quick Panel Removal
Heated Grips
Seat Lock & Practical Helmet Lock
Side Mirrors – retaining & vibration dampening
Windscreen Decor & More
Wind Deflectors
Hand Lever Insulation
Free Upgrades using doughnuts
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Hyperlinks – BMW K100 8 Valve Motorcycle
Maintenance | Parts | Tips & Tricks | Funky Hacks
PARTS & TECHNICAL INFO
MISCELLANEOUS
Recommended Product
For the Month for March 2025 – Amazon Alexa Echo
I set one up in my workshop and it’s a great tool for calculting conversations and leaving notes on parts and repairs. Turning on the lights, knowing the weather, and setting alarms are benefits I really dig. Everyone loves listening to music while wrenching! I have is set up with a British accent and it’s a hoot.
Always shying away from Google Assistant, I took a chance on the Amazon version.
I like technology but as a junior hacker always searching for older proven devices to fix or hack with Linux. Alas at the local 2nd hand shop a score of three Amazon Echoes for only US$19.00- Yippe and wow! As a professional audio technician and computer enthusiast I am super impressed with the sound and different “skills” one can access. Now I just have to get my mom hip to using more often. One might not find them at the sensational price I did but if you have been thinking about a massive life style upgrade, this is it. A lil’ AI won’t hurt.

About Anthony Mrugacz & his BMW K100 8 Valve Motorcycle want you to know the following about links to Amazon products on this website:
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