Oil Consumption K100RS, what is normal?

  • Hi, just recently got my first BMW.

    The previous owner (father in law) stopped driving the bike some years ago as he believed there was an unexplainable oil consumption, which he did not trust....

    The bike has 175K km's on it, and has a beautiful grey exhaust internally (my father in law never drove the bike less then 400-500km's a day, when he drove it), so I do not believe it is burning the oil via the valve seals.

    When starting it up for the first time today in quite a few years, it started immediately, a small puff of blue smoke, but then ran very smooth for about 25min (idling and revving modestly through the gears while standing still on a motorlift). The was no external oil leak to be seen.

    Is there a possibility that the engine oil can leak internally? If so where could it go and how could I check this?

    More in general, how much oil can a bike with these km's consume typically?

    Many thanks, Piet

  • Hey Piet!

    Only 4 more threat and you have access to the download :)

    As per Book (?) max allowed oil comsumption will be 0.0015lts/km

    I never park my K on the side stand. I always put it on the center stand otherwise it will smoke when I start it.
    This is prevalent if the bike is hot when you put it on the side stand. the oil is more "liquid" and will find any crack to sip in.
    The K100 pistons and rings "feature" was corrected in 1988 by the addition of a locating pin for the rings on the pistons.

    Have you checked for oil or water leak under the oil pump? There is a small hole under the engine (see picture below). If any water or oil is leaking there, the water pump will have to be overhauled. Be sure that this hole is not plugged. Use a Q-tip to clean it.


    Cheers espresso

  • Hi Piet,

    heartily welcome to your forum.

    Your bike ist a 1990 K100RS 4-Valve Engine originally painted in silver:

    Fahrgestellnummer 6408338
    Typ-Code 0523
    Typ K100RS (EUR)
    E-Baureihe K589 (VV)
    Baureihe K
    Türen 0
    Motor 4-ZYL
    Hubraum 1.00
    Leistung 74Antrieb
    Getriebe MECH
    Polsterung ( *)
    Prod.-Datum 1990-04-19

    You can check it at the official web-based spare parts catalogue at http://www.bmw-motorrad.de ;)

    Before you start, you should replace all fluids and filters.
    All Oils, Fuel, Brake fluids etc. Also the spark plugs and injectors.

    Then have a look at the rubber stuff at your bike. After such a long time standing the rubber parts could be chapped, so you might have a false air problem.

    Sure, it is possible, that some of the seals are leaking. You have to watch it and replace, if necessary. The mileage of 175tkm ist relative high, but the engine is in a good condition, if maintenance was made periodically.

    Oil consumption of the 4-valve-engines are a bit higher than of the old 2V types. A consumption of about 0,3 l/1000km is considered as normal.

    Don't start a K only for a short time. This is not good for the electronic, especially for the starter relay. A big number of starting procedures will damage the relay and continiuos run of the starter will only stopped by cutting off the battery...

    Axel ... aus Oberfranken - in Bayern ganz oben

    "Die Welt wird nicht bedroht von den Menschen, die böse sind, sondern von denen, die das Böse zulassen."
    Albert Einstein

    neben Moppeds gibt's noch DAS

    Don't :drinkingcheers: and :sportbike: !!

    Edited 3 times, last by mzaxel ().

  • Hi Espresso, thanks, good tip not to put it too much on the side stand (will try it once to see if mine then smokes). I will also check the little hole (had not expected to be Q-tip cleaning with this bike :) )...!

  • wow Axel, that's cool info on the history of the bike..!! I will check the web based catalog from BMW itself....the colour has not changed at least ;)

    Pretty extensive list to change, but agree on the content........ it's a little chicken and egg issue though...... my initial thought was to get the bike through inspection, with minor cost (I had to replace the battery to get it running, but that was all so far, and I think it looks pretty good for the inspection). After it passes the inspection and I get it registered again, my intention was to drive it for ~500km to see if there is indeed an oil problem, if not, do the full maintenance as you suggested.... if yes (oil leak or excessive consumption or misplacement of oil) diagnose the issue, see if it is repairable within (cost) reason, and then if fixed do all required maintenance.......

    What I am saying is that if there is a considerable issue with the oil leak, I am not sure if I want to spend north of a thousand euros (just for example) for a fix, if I can't do it myself....

    Thanks for all advice...!!

  • Oil consumption of the 4-valve-engines are a bit higher than of the old 2V types.

    Sommige noemen de motoren met 4 kleppen "olie-suiplappen". :hyene:

    "Technischer Fortschritt ist wie eine Axt in den Händen eines pathologischen Kriminellen."
    Albert Einstein

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