BMW K100RS Tech Thread

    You must be logged in and belong to this group to post to this forum.
    76 of 92
    caveman
    last year
    Yermo,
    The factory rider's manual (pg. 58) list Max. oil consumption at l/100km = 0.15 so you are still well below that. I agree the the recent increase should be investigated anyway. I would have to agree with chicken that change in oil formation that you are running could very well be the cause and very easy to check. I would try 20-50w non synthetic API SE and SF, the engine was not designed for synthetic and fear of developing sprag clutch problems with it's use. Also checking that the crank vent is not blocked is easy too. But in the end it could very well be time to move on to a different bike, I heard riding a K75 will "ruin" you!
    Cheers
    77 of 92
    Yermo
    last year
    Crank vent!! I had not considered that. If that vent is clogged it'll create back pressure, no? 

    The crank vent had come unattached and I reattached it at the same time as the last oil change. I wonder if maybe I missed some crud in the line since it was quite challenging to get the thing back on. 
    78 of 92
    caveman
    last year
    I would unattach the vent again! If I'm not mistaken the original vent (crankcase) goes through the fuel tank vent with a check valve that can ether hang up closed causing crankcase pressure or hang up open causing fuel vapor (or raw fuel if full tank) to be drawn into crankcase; nether being good for the engine. So I would ether vent it to atmosphere or to intake track.

    BTW I know you took a short ride on a 75s (in NY)... maybe that did not move you to explore the other option? 

    Cheers
    79 of 92
    Yermo
    last year
    I will check that out. Thank you for the pointers. 

    The K75S is an impressive machine but I still like my K100RS. :) 
    80 of 92
    Yermo
    last year
    I came across this document today:
    81 of 92
    Yermo
    last year
    I'm building up the motivation to start delving into the oil consumption issues on the Beloved Blue Oil Burner. With 125,000 on the clock, valve stem oil seals are the likely culprit. It's burning oil mainly on deceleration which implies oil is getting sucked past the valve stems because of the vacuum that's generated while decelerating off throttle.

    82 of 92
    Yermo
    last year
    There's a K bike owners group on facebook. A question was asked about the Laminar Lip I have on mine when I realized that I not posted the link here:

    Link #63532
    Yermo
    last year

    Laminar Products for BMW K100RS-K1100RS

    This makes a huge difference in the buffeting these bikes generate.

    https://www.laminarlip.com/k100rs.p...
    83 of 92
    Yermo
    last year
    Link #63535
    Yermo
    last year
    84 of 92
    Yermo
    last year
    So instead of riding, buffalo and I started to tear into the oil consumption issues on my long suffering oil burner. We managed to pull off the top of the airbox which houses the "cyclonic separator". It at first appeared that it could be taken apart but it looks like it's installed before the part is glued.

    We found some pictures of it here:

    85 of 92
    Yermo
    last year
    Diagram of a modification to the crankcase breather system in the middle of this page:

    86 of 92
    Yermo
    11 months ago
    A description of the valve check procedure of the K100RS:
    Video #65241
    Yermo
    11 months ago

    BMW Service - BMW K75 & K100 Valve Clearance Check

    Checking the valve clearances on a 1985 K100RT. This applies to all K75 models (1986 ~ 1995), all K100 models (1985 ~ 1990) and is basically the same for the...
    87 of 92
    America.Rides.Maps
    11 months ago
    Are you swapping engines?
    88 of 92
    Yermo
    11 months ago
    America.Rides.Maps, yea, that's the plan. To do a rebuild on the engine I have is silly expensive. 

    I have two parts bikes. One runs. One has been sitting too long. Sadly, both have compression numbers that give me serious pause. I've been doing some reading to convince myself that I'm not misinterpreting the numbers or making some mistake.

    Ideally, I'd like to do the engine swap once. On this bike, the engine is the center stressed member so it's more like you swap bikes around an engine. It's a pretty big job. 
    89 of 92
    Yermo
    4 months ago
    It dawns on me that I haven't posted anything here about the massive Oil Burner Engine Swap Project of 2019. 

    After a lot of soul searching and upon strong recommendations from experts, I decided to swap engines instead of trying to fix/rebuild my engine.

    My best guess is that the increasing oil consumption and fouling of plugs is due to valve stem seals failing and this may all be due to running the engine with a failed open thermostat for way too long. The problem was obscured by a temperature gauge that wasn't reading properly.

    The donor bike has only 38,000 miles on it. The question was asked as to why I don't just run that bike instead? 

    Blasphemy!! If I were to do that then it wouldn't be my bike.

    So where we sit now is that both my bike and the donor bike are disassembled off the frame. The frames are hanging like carcasses in my garage. My engine and the donor engine are on the workbench and I'm starting to slowly clean and re-assemble things.

    A smattering of photos, sadly not in chronological order:

    Photo #69806
    Yermo
    5 months ago

    Photo #69808
    Yermo
    5 months ago

    Photo #69811
    Yermo
    5 months ago

    Photo #69807
    Yermo
    5 months ago

    Photo #69810
    Yermo
    11 months ago

    Photo #69809
    Yermo
    5 months ago

    Photo #69816
    Yermo
    4 months ago

    Photo #69815
    Yermo
    4 months ago

    Photo #69814
    Yermo
    5 months ago

    Photo #69812
    Yermo
    5 months ago

    Photo #69813
    Yermo
    5 months ago

    90 of 92
    Yermo
    4 months ago
    The fuel lines on the donor motor are rock solid and the factory BMW lines are no longer available. Asking in the K100RS group on Facebook I was told to look for "Sae30r10 fuel line" which is apparently the spec for submersible lines in the fuel tank, which will also need to be replaced. It's an 8mm interior diameter.
    91 of 92
    Yermo
    2 months ago
    Just leaving myself a little note as a reminder. There are thin o-rings between the throttle body bases and the cylinder head. The BMW Part number for these is: 11 61 1 465 169

    "AIR INTAKE MANIFOLD TO CYLINDER HEAD O-RING"

    It took forever to find them since they are listed on a non-obvious fiche.
    Link #72302
    Yermo
    2 months ago

    K 100 RS (4V), 1989-'92 | Bobs BMW | Bob's BMW

    Search BMW Part illustrations for K 100 RS (4V), 1989-'92 . Thousands of BMW riders nationwide have come to trust Bob s as their prime source for motorcycle parts, accessories and apparel.

    https://www.bobsbmw.com/store/micro...
    92 of 92
    Yermo
    9 days ago
    I took some time out from mobile app development and added a set of features to the site where we can organize, plan, and document wrenching projects ... and in the process not have to fill this forum up with things people might not be interested in  ...

    Yermo
    14 days ago
    Project (74721)
    The Great BMW K100RS 16V Engine Swap Project of 2019

    The Great BMW K100RS 16V Engine Swap Project of 2019

    My '92 K100RS 16V with 123,000+ miles on it started  significantly consuming oil and fouling plugs. It started smoking dramatically on deceleration as reported by Duncan. A compression test and leakdown showed a variance of more than 20% between the cylinders. My best guess is that two things failed in concert: the thermostat stuck open and the temperature gauge did not read accurately. As a result, the theory goes, I ran the bike too cold for probably too long and that caused it to fail.

    I had picked up a spare identical bike because I wanted to swap out the fairing since mine had started looking pretty rough. The donor bike is actually in much better shape and a saner man would just have attempted to transfer parts from my bike over. But as it turns out the donor bike also needed the water pump rebuild, the rear main seal, and other work including cleaning up evidence of some monkeying by previous owners. 

    As a result, I made the decision to disassemble both bikes and create one decent machine from the best parts of both bikes. We made short work of the disassembly but then with distractions the project has lingered. Time is getting tight as Bruce is going to be flying into town and the three of us hope to go on a multi-day ride. If need be I'll ride my DR650SE but ideally I'd like to have my Beloved Blue Oil burner back in service before then. 

    To make the job of coordinating parts, tasks, information, and documentation, I've taken a few days away from banging my head against the mobile app development wall, and built out a project/build feature which months ago I had discussed with Mike. It's super rough at the moment but it presents the beginning of a place to thoroughly document one of these big projects along with all the associated rich media that goes with it. My hope is that it's going to be useful. 

    formVistaTM By: Flying Brick Software, LLC
    formVista generated this page in: 0.2883 seconds
    using '6291456' bytes of memory