UPDATE 18 February 2026 – start easily- no screeches, leaks, nor imbalance. Injecting 10cc of motor oil into the cylinders before start up to help compression on a enging that’s been sitting awhile surely helped! See the video.
The winter of 2025-2026 in my unheated garage is perfect to perform “Operation Revive” on my 1985 BMW K100 with 133,500 miles on the odometer. The local BMW dealer wants aroud $225 per hour work on classic bikes and really doesn’t seem interested in doing it all. Alas left to my own devices armed with repair manuals, Internet forums, and mega shopping websites like Amazon and eBay, it’s time to tackle the challenge. Least I forget EuroMotoElectrics.com as a great alternate for BMW motorcycle parts.
Operation Revive, a two part project, starts at the rear of the enine. Part 1 addresses components such as the entire clutch assembly, main engine seal, along with all the bearings/seal on the starter/alternator auxilary shaft on the rear of the engine (view exciting pics). On the front of the motor Part 2 will change the timing chain, oil seal, and three (3) guide rails as the are still all original. So let’s see what it all costs and the tools I needed to obtain.
Wham Bam No Thank You Mam!
Tariffs and BMW’s “Break My Wallet” parts policy was a challenge. Here’s a breakdown of expenditures versus what would have been. My secret to saving money on BMW K100 Operation Revive is below this table of expenses. Which by the way was $1,832.70.
| Part | BMW OEM- $2,292.30 | Alternate -$459.60 | Source |
| rear main seal | $57.86 | $29.99 | EuroMotoElectrics |
| clutch plate | $503.39 | $62.34 | eBay |
| clutch spring | $208.20 | $62.34 | eBay |
| clutch pressure plate | $436.84 | $62.34 | eBay |
| clutch housing cover | $493.74 | $62.34 | eBay |
| clutch o-ring | $3.38 | $1.81 | Amazon |
| clutch compression ring | $25.91 | $15.00 | EuroMotoElectrics |
| clutch nut | $22.21 | $19.00 | EuroMotoElectrics |
| clutch mount bolts (6x) | $110.10 | $17.95 | EuroMotoElectrics |
| front engine seal | $43.35 | $10.45 | eBay |
| timing chain | $164.70 | $79.99 | EuroMotoElectrics |
| chain guard rails (3x) | $79.38 | $68.87 | EuroMotoElectrics / eBay |
| auxilary/alternator shaft seal | $64.41 | $12.55 | Amazon |
| bearings; auxilary/alternator shaft (4x) | $158.21 | $23.50 | Amazon / eBay |
SIDE NOTE: Installed a new clutch cable I had sitting around for 20 years and swapped the driveshaft with a low mileage unit (33,000 miles). Driveshaft on eBay was just under a hundred bucks as comapred to $900 for a new one.
My Advice for Best Prices on new parts for BMW K100 Operation Revive
- eBay Bookmarked Search – Daily check items posted for sale, here are my parameters
- In the search bar for eBay Motors the text “BMW K100”
- Select Brands checkbox – BMW and Bosch are my choices
- Sort by Newly Listed
Take a look at my saved bookmark using the above parameters.
2. Alternate Parts source (US based)
- EuroMotoElectrics – OEM and Aftermarket
- Usually has a sale around Thanksgiving and Christmas offering free shipping or small discount.
3. Parts substitutions and searching the behemoth Amazon.
BMW builds motorcycles and outsources for many parts. Sure, there very good websites to find information for my K100RS; Max BMW Motorcycles and BMW Motorrad are two prime examples. I could list all the bearing and seal sizes here but hey, do some research and learn something new.
However, one may come a across a situation where a part is listed “Not Available” (N/A), especially for bearings. My solution is to use an older BMW parts calatalog for my 40 year Beemer.
Nuts, bolts, seals, o-rings, and bearings, once one knows the brand or manufactures plus sizes and material, items can be obtained on Amazon. eBay, or your local hardware store.
Remember- plan. Time is a money saver.
Mechanic Tools Obtained BMW K100 Operation Revive
Estimate addtional expenditures for tools: $85.00
Soon to add pictures and additional text.
- Bearing Extractor – a communist-made $25.00 “motorcycle” bearing extractor worked flawless.
- Heat Gun – essential to heat case to 225F°, I used a Black & Decker costing forty bucks.
- Seal Puller – Gets the job done in the spirit of “easy peasey, lemon squeezey”.
- Main Oil Seal Install Tool – eBay 3d printed, under $20 & I desired getting the seal in purr-fectly.
- T30 socket to remove bell hosuing/intermediate flange bolts
- Scotch Brite Pads – essential for removing burrs and old gasket material.
- Tennis Ball – used to balance the clutch kit (see video below); I went for the “Wilson Championship” model.
Pictures & video soon…
Choosing the Right Chemical Products
Estimate addtional expenditures for chemicals: $20.00
RTV Silicone – MOPAR 4883971 RTV Silicone Rubber Adhesive Engine Sealant – 3 oz. Tube
Taking my time to do all these repairs I explored different RTV silicone products. This video on YouTube gave me great insight into various brands of sealant. It tested and rated well in the video and the deal maker was the resistance to alcohol infused gasoline (E10) like those we find here in Ohio. Sadly, my state like many others, does not require fuel stations to label these fuels. My main concern is sealing the bell housing properly as the bike needs to be disassembled to access it. Sure don’t want to redo the seal on it!
Assembly Lube – Permatex 81950 Ultra Slick Engine Assembly Lube (gets great reviews!)
There were some essential parts which need to be pre-oiled when replaced before initial startup of the engine. However, if the oil dripped down while assembling, it would probably ruin the RTV gasket sealer too. Not needing a leak after all this work, a couple of dabes of assembly lube to certain shaft and bearings to resolve. The Permatex 81950 is tacky and will help hold part 19 during install.
Acetone
Cleans like the Dickens! I soaked my starter sprag clutch in it. All parts needing to mate precisely, engine covers and bearing, had there surface cleaned with acetone and a gentle rub with a Scotch brigh pad. Then rinse with brake cleaner and dried with a lint free cloth. Acetone can be obtained inexpesnively at a discount grocery store often labeled as “nail polsih remover”. I pay less than two dollars for a pint. Fabulous cleaner but careful, it’ll remvoe paint.
Checking clutch balance with limited resources
Installing a new complete clutch kit in my1985 BMW K100RS became a challenge when there wasn’t a paint mark to heavy side on the CLUTCH HOUSING (BMW part# 21 21 1 450 899). The new PRESSURE PLATE (BMW part# 21 21 1 464 570) and the HOUSING COVER (BMW part# 21 21 2 333 472) did have factory paint marks making the experiment easier.
A new Wilson tennis ball was used on the smoothest level surface available (the kitchen table). First I spun the CLUTCH HOUSING to fine the heavy side. (several times). It will be the side that falls to the surface, Secondly I spun with the other two parts with the marks 120 degrees apart from each other and the clutch hosuing. After a few combinations and severals spins to check it- voila! The best balance I fell I am going to get. It’s mid-winter with a foot of snow plus it hasn’t been installed yet to check for vibration. Once installed I will edit this with the results. NOTE: I read this on the Internet but no video or pictures were posted with it hence my video showing the results.
PART 1 – Rear Engine Photos
All back together and no leaks!
Start up without the Staintune muffler- yee haw!
Yes that is snow in the background and it’s -25° Farenheit!
Part Two – Timing Chain & Guide Rails
Not fun working on a motorcycle engine not on a lift but we were gifted weather averaging 55F° for a few days. New timing chain and three guide rails installed and running mucho quieter. BMW Motorrad states it needs changing after 60,000 miles but alas I say go for double that. Waiting like I did was psuhing it but the new quietness on the front end (along with four new bearings on the back end) sure adds confidence this Beemer will go another 100k+ miles.
Lookie here- comparing a new timing chain (top) versus one with 133,500 miles (and a bit noisey it was).
BONUS: Sidestand rebuilt and it’s better than stock – learn more…
Why not visit one of my worldwide Amazon stores today as sales support the maintenance of this website.