Hi everybody,

I am currently looking for a K100 LT or RT. A few years passed since the last time I rode a motorcycle, but before the abstinence period I have logged some 15 years and 100.000k + on various motorbikes, one of my most loved ones was an ex-police air-colled R80 RT.
Since i have 6 weeks on-10 days off work schedule, I wont be using the bike that much, but still want to be able to do some turing with my kids, so a brick seems a good choice. I am aware of the splines issue, ABS warning lights (if applicable), weeping holes on the front and back and the necesity for the bike to have regular maintainace records. Any other issues I should be looking at when inspecting the bike?

Looking forward to riding again:)

Welcome Tarlin. Good luck searching for your next bike.

On the Portal page, you'll see Forum links: Click on You just bought a used K100, so what now?


Hopefully it'll answer most of your questions.

thanks BlaKey, that was fast and a lot of useful info in the link you provided. Really appreciated!

I went today to see one K100 from 1988. The owner was really busy, so I had only sort time, and due to heavy rain and a worn out rear tire I have opted not to take a test ride. There were a few issues with the bike: The ignition lock was broken, and the part where the lock is located has been broken off from the instrument cluster, as the owner needed to get home, so he broke the lock and hot-wired the bike. Also no records of the splines being lubed. I have tried rocking the wheel but found no freeplay at all. Is there anything else I can do to check the splines beside removing the wheel? The "weep" hole on the bottom front part of the engine seemed dry, but there was some oil on the seal between engine and transmission (see photos) Is that a problem?

sorry, still learning how to post properly:)

I took the plunge, and bought a 1987 K100 with 59k km today:) On the picture, the bike is still complete, on the way home Ilost the left side cover (plastic). I was so angry, but...I guess I will have to source one:). First question (many many more to follow sure:)): when running, there is a sound like vacum is beeing created(suction) somewhere. Any idea what that could be? Some deteriorated rubber somewhere? Bike runs ok, just at idle it is not 100% smooth, but the change in revs is minimal (not noticable on the rev gauge)

Nice bike. All the rubbery components of the inlet tract are probably 30 years old so need checking.
Go to the Portal and have a look at So you just bought a used BMW Ted has some good reading there for first time owners.

Hi Tarlin,
1st order is to peruse this site as their are many people that have very valuable information, and in the long run a little searching will save you lots of money.
As suggested the rubbers might be perished so motor works or motobins will be your best bet for spares. A full service before you do serious miles /kms would be advisable. These bikes like to be ridden and if you service them regularly they will give you years of service.
Enjoy
Mike

It looks a nice K there, sorry about the plastic cover too.

Just be careful as the design of those covers changes over the years and not all are interchangeable.

Don't over fill the engine oil when you do a service, also some of us are finding fully synthetic oils get past some of the seals, maybe semi synthetic might help. The sight glass on the right hand side of the sump under the engine, the red dot is your ideal, but do not fill above the red outer circle.

Rubbers and seals are your biggest issue due to age and that includes the tyres, often left to go too old. Seals inside brake master cylinders and calipers may need doing. I have put almost 50,000 miles on my RT and been in to all the known K issues at this time but not have to do any of them twice, just keep riding and they go forever.

With the help of the forum for knowledge and advice on where to get parts its not expensive or difficult to keep it in top condition. There are often new parts available for less than the price of used BMW parts so ask on the forum first. Common items like fuel pumps, clutch plates and cooling fans being some of the most common.

Tarlin wrote: First question (many many more to follow sure:)): when running, there is a sound like vacum is beeing created(suction) somewhere. Any idea what that could be?

I heard that sound once. It was made by money leaving my wallet at a BMW service counter.
Haven't it heard again for years since I started doing my own maintenance. 

Welcome, Tarlin!

Tarlin, there are some useful links for ordering parts, much better and cheaper than official BMW network:

www.motorworks.co.uk - new and used parts

www.motobins.co.uk - new parts

www.siebenrock.de - luggage - top case 50 ltr

Try to find some good (older mecchanic) in Ljubljana (once Tehnounion was only representative of BMW in Yugoslavia)

There are some technical back up here in Croatia, be free to send me an email. You bought very nice bike, 60 tkm was runnning in.

Tarlin, that's a nice looking bike! 

I don't know about your part of the world, but I have had excellent luck finding a lot of the new and used parts I need at very good prices on eBay.

First of all, I really want to thank all of you for responses and advices! I managed to found a K100 enthusiast/mechanic, and the bike is in his hands now. I would love to do all the work myself, but I work in off-shore, and I left my home just a day after my purchase, so it was not an option, especially since I wanted to ride the bike when I come home. The mechanic has been nice enough to send me some reports with pictures about the progress. The bike is a solid base, but it shows that it has been sitting in the garage for the past few years. The oil change was done last year, but regardless, all the fluids are going to be replaced, including the fork oil. Splines are in good condition and have been lubed  . There is of course a couple of rubber parts that have been ordered and will be replaced, and the fork bearings became stiff as the grease dried out. Also the break pads have been replaced, the old ones had enough meat left on them, but were squeaky as hell . He also had a side plastic and a missing lock for the luggage in his used parts inventory, which means all I need to do is ride it when I come back home in a couple of weeks

Best of luck with it and even better it sounds like you are in good hands.

If you are going to do a spline lube at the front end as in clutch splines you will get to see how the clutch is. Mine got replaced at about 77,000 miles and I guess about 5k miles was left in it so its good for about 125,000 km. It could be worth doing clutch and rear main seal/clutch O ring as a precaution if you are in there. The rear main seal will go at some point, mine was weeping for a while but it kept the clutch splines in good order.


Also be sure to replace the fuel hoses outside the tank, they all go hard and crack and the movement of tank off and tank on is likely to finish them off and cause leaks.

Thanks Olaf, will make sure to replace the rubber gasoline hoses, good point!!

If you make them a little longer you will be able to slide the tank back enough to access the radiator cap without disconnecting the fuel lines, also you will be able to lift the back of the tank to access the electrical relay box and relays without disconnecting the fuel lines. Store some spare bulbs in the electrical box.

Laitch wrote:

Tarlin wrote: First question (many many more to follow sure:)): when running, there is a sound like vacum is beeing created(suction) somewhere. Any idea what that could be?

I heard that sound once. It was made by money leaving my wallet at a BMW service counter.
Haven't it heard again for years since I started doing my own maintenance. 

Good answer!

A part the links given to you, after running my own business in independent BMW workshop, I strongly suggest you to order your parts at BMW dealer. They're usually cheaper than  motorworks, motorbins or siebenrock, and, professionnally talking,  I had a lot of quality issues with aftermarket alternatives these independents propose.
You even can order directly at  BMW Classic. Genuine parts, free return, guarantee and free sending costs from 70€. Sometimes, parts ordered there are coming to you in several parcels, not delivered together but it's due to the way this service works: if the part is not available in their stock, they'll ask fort it in the BMW network.

92KK 84WW Olaf wrote:If you make them a little longer you will be able to slide the tank back enough to access the radiator cap without disconnecting the fuel lines, also you will be able to lift the back of the tank to access the electrical relay box and relays without disconnecting the fuel lines. Store some spare bulbs in the electrical box.

Thanks Olaf, thats really sound advice

I had breakfast with a few riders yesterday and the subject of fuel hoses came up.

Sound advice jbt.

I said that when I had done mine I bought a 1m length of 8/13 from the local BMW dealer for €19. Anyway one of the guys rubbished the idea and said it was daft but for me the only place I use that hose is on the K and have no other use for it so no point in buying more of it.

Anyway his comment was that he got hose and finds it only lasts less than a year but that its a much cheaper item. Anyway a quick look revealed his cheap hose was not a correct one and was breaking down, wasn't for fuel injected systems and was for diesel fuel which wasn't a difference I was even aware of. Why? Because for some things the BMW dealer is indeed the right place to go.

I use original BMW clutch cable, just compare the original and others side by side.

Fuel pump I will happily use a different one simply because the original isn't even a BMW one, its Bosch and lots more out there.

I had a bad experience at one long established BMW motorcycle dealer over here, rang for a part they had 'in stock' and it took 3 weeks to come when I could have had it off Motorworks in 2 days for less. Thing about Motorworks and Motobins and no doubt siebenrock is that they do have the parts in stock. I have phoned Motorworks on a Monday afternoon and had my parts on Wednesday morning in regular mail, in a different country to Motorworks.

Well, the bike is ready now, added the original top case, but due to a broken shoulder (MTB accident) it is sitting in the garage. So I decided to "improve" it a bit, by adding LED lights to the instrument cluster...and managed to break the speedo in the process... Oh well...I hope I can post better news soon, and some pictures from the bike, ready to go.
And I have found out that the first registration date is 01.07.1987, but when I enter the VIN number to the bmp-classics.de it says it is a K100 RT 84 ECE.
Thanks again for all the help and support!!!