BMW K100GSA Project

Discussion in 'Some Assembly Required' started by Wiz (J.C), Sep 2, 2021.

  1. Wiz (J.C)

    Wiz (J.C) Adventurer

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    Currently my project is in a ridable state, this is how I got there.


    Ill start at the beginning, I was browsing craigslist for cheap bikes, looking for something most would call a basket case, and I found one, it was a k100. Now, I had never heard of a k100 before but even in its sad state the unique engine placement caught my eye.

    Fast forward a week and it was mine for the grand total of 500 dollars. Here is what she looked like the day I brought her home.

    0823191131_HDR (1).jpg

    I began taking the old girl down to the frame, inspecting as I went. Cracked intake boots, dirty throttle bodies, leaking fork seals, the works. I stripped the frame and painted it (intending to powder coat eventually) and I took the engine down too. Replaced rings, valve stem seals, lapped the valves so they sealed nicely again, painted the engine covers.

    0828191115_HDR.jpg
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    1031191352.jpg

    After I got most of the mechanical issues sorted out, I began working on installing a new ecu. I chose to use an MS3 Pro.

    0810201646_HDR.jpg
    0810201646.jpg
    1017201038.jpg

    This was the first first iteration of my ecu Implementation , I end up relocating the ecu and using the original electrical box to tidy up the electronics.

    I have also installed a custom modern ABS system, this is something I am still doing some work on, but soon to be worked out hopefully.

    Going into some more detail for the ECU conversion, I made my own harness and the parts I used to adapt the MS3 pro to a K100 are below:

    BSK speedworks Toothed wheel crank sensor kit

    TPS Part number: Hundai 3517022600 (This fits on the stock 8v throttle body with no modification, the only custom part needed is a very simple adapter plate of approximately 1/4 inch thickness that cants the sensor forward so the sensor will work with the rotational range of the throttle body, alternatively one can use a set of 16 valve throttle bodies and tps sensor such as is used with the BSK speedworks kit)

    Coolant Temp Sensor (exact same form factor and thread as stock, but is a single element unit compatible with modern efi): Bosch 0280130026

    Intake air temp sensor: GM Temperature Sensor 25036751 (installed in a 3/4 NPT bulkhead fitting in intake manifold)

    Coil pack: VW 4 tower wasted spark coil pack 032905106E (This coil pack fits rather well in the area that the OE coils did, is cheap, and has an igniter built in, greatly simplifying wiring, for any others looking to do this, for a higher price and less custom work, BSK speedworks offers a similar kit with mounting bracket and leads already included and ready to wire to any ecu)

    Plug wires: standard plug wires from a vw jetta, cut and harvested coil ends, and

    As for the airflow meter, its gone (for sale if someone wants it, good price too), I am using tuner studios ITB tuning mode, which uses a blended table of manifold absolute pressure (Speed density) and throttle position(Alpha-N), so I have a silicone 90 and a filter affixed to the airbox where the airflow meter would be. This tuning mode uses SD at low load, high vacuum engine states, and once MAP reaches 90% barometric (90kpa) it switches to Alpha-N tuning. The reason for this is because tuning with just SD leads to issue tuning WOT, as for the latter say~30% of throttle will have very little change in intake vacuum. IIRC, the 16valve bikes with motronic ecu's use this same type of tuning algorithm, as do many modern efi motorcycles.
    Now, one could replace the airflow meter with a modern MAF and tune that way, but I elected to go with the ITB mode for a cleaner look and more flexibility with the tuning as Tuner studio has a dedicated mode just for that specific application.


    For the MAP I have bridged all the throttle bodies balancing ports together and run those to the fuel pressure regulator (stock) and then to the MAP input on the MS3 Pro Evo, reason being it provides a better average of the whole system that just one cylinder, and smooths the input into the ecu.


    Now, I decided to go in the direction of an adv build a while ago, so I picked up a set of ktm 1190 adv r forks, and have custom trees made for me by cognito moto in VA. Very nice build.

    Here is the bike with the new front end installed.
    0902211554_HDR.jpg
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    I am currently having a longer rear shock made. At full extension it will raise the bike up about 1.75 inches from stock. This is where my project sits now, I have ridden it 3 times now, and I am working on dialing in the tune for the engine. I data log my ride on my phone, and then analyze the logs when I get home, and make any changes to fueling or otherwise.

    In the future, I am getting a spoked rear wheel made, and I want to make a rack for luggage on the back. I have noticed that the handlebars vibrate alot, so I am also installing a damper soon. I also have ordered a front fender to install on the bike.

    Thanks for anyone who has read this far, have a nice day.

    Wiz
    #1
  2. Franque

    Franque Nilé na sohakélwa manga

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    Wow! That's a really interesting project, I'll be following along!
    #2
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  3. sruss67

    sruss67 Been here awhile Supporter

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    Hey Wiz, that is incredible, nice work you are doing.
    #3
  4. Jim K in PA

    Jim K in PA Long timer Supporter

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    Welcome to the asylum. Excellent introduction, and very cool project. What year K?

    I, too, picked up a "basket case" K100RS a couple years ago and have been finally riding it this season. Great bikes. How many miles were on yours when you got it? Mine had/has ~43k, and when I pulled the head to replace the head gasket, the top end and cylinders looked as new. I was surprised yours needed parts/work. These engines go very long distances without major repair or rebuild. IF maintained properly.

    Local inmate @Arktasian will be interested in your FI updates. He is doing something similar to a K75. He also built his own MS system for his FI + turbo airhead. ;)
    #4
  5. Arktasian

    Arktasian Feelin the BMEP

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    Wiz, nice looking work & sounds like you have the bases well covered, for a reliable MS system. Have you done any tuning before on them? I'd be happy to discuss things, I'm no expert but about 10 years playing with a V2 version/ Microsquirt on a boxer airhead has been a hoot and productive.
    My K75 being 3 cylinder has differences to your 4 lunger, key being the need for a cam sensor to allow sequential fuel injection (the reason for that I can outline).
    All my parts hand built, apart from the turbo's. Yup, turbo on the K75 too .
    I can't hold a candle to the likes of Allen Millyard, but do seem to be able to integrate things for a stock look where people viewing ask about "that bolt over there".
    Looking forward to seeing more!
    Lorne

    PS - my handle on the MS forums is "R100RT"
    #5
  6. 3legs

    3legs Real men ride sidecars Supporter

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    A piece(s) of advice for you. Have a look at the fuel pump plug underneath on the LHS front of the tank. From memory it's a 4 pin round plug.

    Give that a really good clean and some WD40 and make sure the male to female pins are tight.

    If they are loose you WILL have intermittent fuel problems. You will be riding along and then all of a sudden you will have no power then just as quickly it will come back on again.

    A bloody pain in the arse and if you don't know about it you will tear the bike apart trying to figure it out.

    I'm not an expert in fuel injection so from what you have said so far I'm not sure of you are using the original ECU. If you are I would suggest you strap the big black plug that plugs into the ECU with some zip ties.

    If not they can sometimes unplug themselves and the bike will either die or run on 2 cylinders. Again an easy fix.

    Also if you find you can't seem to get full power through the rev range it could be your in tank fuel filter has split. I'd put in a new one now.

    Fuel pump, from memory Ford make one that is a 1/4 of the price of the original BMW.

    Drive shaft, make sure the splines have been greased with the correct grease ( can't remember the correct name but I think it was that white shit ).

    Final drive, take it off and inspect the bearing and the gear teeth. They were the weak point in an otherwise reliable bike.

    Change your final drive oil every 5000km's. Doesn't take long to do and will increase the life of the final drive.

    I've had a couple of K100's and currently have a K1100 that takes me on roads that I shouldn't be on and they are an extremely reliable bike. With some simple maintenance they will never let you down.

    Here's a pic of my K1100.

    img_0411.jpg
    #6
  7. Wiz (J.C)

    Wiz (J.C) Adventurer

    Joined:
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    A big thanks to everyone for commenting and welcoming me.

    I will answer some questions from the above posts.

    @Jim K in PA
    As far as the history of this bike: California emissions spec'd K100LT, built Berlin 7 Nov 1986, but delivered through BMWNA in New Jersey on 17 August 1987, Bahama Bronzit metallic code 636, with no listed option bar the CA spec.

    I have no idea what the true milage is, the cluster was not original, and the bike had been on non op for so long, that information was long gone from all records when I bought it. In light of this, even though I probably didn't need to tear the engine apart, I did. The original plan was to just replace stem seals and lap the valves, but, while I had everything torn apart I figured I would check up on the piston skirts and rings, and check out the bearings. I ended up breaking one of the rings, so committed to replacing all of those, then while I was checking bearings I found one that was more worn that I would have liked. After that I just replaced the all big end and main bearings out of principle.

    @Arktasian
    I have never done any tuning on anything before this project, no. I decided I would learn with this project. So far its been a lot easier in practice than in theory, which is nice. That being said, I am still new to this, so there is always more to learn. If you are so inclined, or anyone else for that matter, feel free to browse through my current tune files Here.

    @3legs
    Actually, all of the wiring in my bike is new. I made a new harness and used almost all deutsch DT series connectors, so no worries there.

    I also replaced the pump and filter in the tank.

    The ECU is now an MS3 Pro EVO, which has really nice water proof connectors.

    As for the drive shaft, I did the wet spline mod. If you haven't heard, you drill a hole in the swing arm on the top to fill and thread it for a plug, then put some RTV on the mating flange with the final drive and fill with a small amount of gear oil.

    Since I needed to replace my final drive cover I did inspect my crown gear and pinion, they both looked great. The reason I replaced the cover. My custom spoked rear wheel is being built on an r1200c hub I had machined down by 5.5mm. This requires the brake rotor carrier from an r1200c as well, and this takes the same caliper as a r850gs and some other older bmw's, so I replaced my cover with an r850gs cover to fit the caliper.

    ------------------------[And another update]-------------------

    Today I rode about 30 more miles, got some lunch, hit some twisties and headed back home, that put just over 100 miles on the bike since the rebuild and all the work shown above, so I drained the dino oil I had for break in and put in some motul 20w50 full synthetic, and a new filter. After I fired it up, the oil pressure jumped right up to 72 psi as it normally does.

    When I analyzed my logs from the ride, I got some more good data all the way up to about 9750RPM (I set my hard limiter to 10000, since the piston speed is within tolerable spec, and I wont be there very often), as well as alot of cruise data (i am running about 15-16 afr for cruise).

    Over all so far, bearing in mind I never really rode this bike before it got torn down, it feels slower than I was expecting, maybe that's just these bikes, maybe that's my timing( wide open timing goes from about 30 degrees at 6250 up to about 36 degrees at 10k rpm), not sure. My full throttle afr is set to 12, and I am hitting that, so that should be good.

    Over all, still good progress!

    Wiz
    #7
  8. Arktasian

    Arktasian Feelin the BMEP

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    Took a look at your files & msq, you seem to have a pretty good balance of settings. Did you try other methods prior to "ITB" for your fueling? I've been with straight speed density from the beginning, which was a recommendation for boosted applications. I'm going to have some bonus tuning time on my hands soon and I was going to do blended tables AN/ SD but may give ITB a shot. The twin lung is rather more resonate on its map readings but there are ways to calm before getting into lags and such.
    I would agree - you have made good progress (don't having remembered even seeing you ask any questions on the MS forums)
    Couple of shots
    IMG_4675.jpg
    IMG_4676.jpg
    The K75 is still in pieces, on my mod table
    #8
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  9. Wiz (J.C)

    Wiz (J.C) Adventurer

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    @Arktasian

    That's a very clean looking turbo install, how much power are you making?

    I went right to ITB mode, seemed like the best option.

    From my understanding ITB mode was indeed for NA installs. I'm not sure how it would work with FI. May work with multiply map enabled, but don't quote me on that. It is AN/SD bases so, it might work.

    I am not a member of the Ms forum actually, and I haven't really had any roadblocks in the tuning or install process, it has gone quite smooth so far, so I never really had a reason to sign up I suppose.
    #9
  10. Jim K in PA

    Jim K in PA Long timer Supporter

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    Boosted Black Betty. :raabia
    #10
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  11. Wiz (J.C)

    Wiz (J.C) Adventurer

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    A Slightly more technical post here. Now that my tune is dialed in enough that the bike runs well through the whole rev range, I am going to configure the most important part of the ITB tuning mode, which is the TPS @ %Bare switchpoint graph. For me I am using the default 90%. The way I did this is to go and ride around for a while to gather data all over the rev range. I then opened the log in MegaLogViewer MS. If anyone else wants to do this a really easy way to get an idea of this line is to use a scatter plot and filters.

    I opened the whole log in the scatter plot and set my X axis to RPM, the Y axis to TPS% and the Z axis to MAP.
    After that I set up a custom data filter for the plot that filters all data that is not between 88 and 92 kpa MAP. (That looks like this in the filter menu set up: [Field.MAP] < 88 || [Field.MAP] > 92)

    After I set this up and apply that filter we get this:
    I have drawn an estimated "Line of best fit" and this is what I will attempt to enter as closely as possible into tuner studio.

    %Baro Switchpoint Scatter plot.png

    Creating this "Line of best fit" to this data, If I could/knew how to do this in the log software I would, but I don't, so I will just be guessing, essentially, drawing an imaginary line from one end of the data to the other, where the line passes through the statistical average of the whole data set. IF we wanted to get all technical about this, we would make an actual line of best fit based on each of these data points, but that's a lot of work, so the estimate will do.

    You can either enter the data as you see fit for each box in TS, or take the first and last data points and interpolate between them, I chose to interpolate since it is faster.
    Regardless of the way you choose to enter the data, you should end up with a good representation of the line of best fit for your engine. Now that I have entered my data in my ITB load settings look like this:

    ITB Load settings.png

    Now I will need to retune a lot of my VE table, but this should allow the bike to run better over all, improve throttle response, etc.
    #11
  12. 3legs

    3legs Real men ride sidecars Supporter

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    You lost me at the word "technical" :lol3:lol3:lol3
    #12
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  13. Arktasian

    Arktasian Feelin the BMEP

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    The fact that you’ve dialed in your hardware and then settings in such a dedicated manner without forum help is excellent- and a huge testimonial for MS. (is your name Sheldon?)
    One of the under appreciated and understood aspects here is that you can dabble in any tuning strategy or settings, save them to your tune files (msq’s) and use them or revert to other known successful settings in a matter of seconds. Years ago I used to get frustrated with carb operational comebacks at our business - these days I take a wide berth from forum chat dealing with jets, needles, and flying blind while AFR’s do their own thing.
    But I digress (& not making friends deep in Bing country)
    I’m about a hundred ponies - their is a lot more available but I like the predictability of this spool up behaviour (7psi - have tested to 22psi) & the “Rubber Cow” is better behaved as such. (I tune with lap top on quiet country roads, auto tuning, logging, and occasionally entries on the fly as lap top straddle mounted over fuel tank)
    Can’t speak for others but I may plagiarize some of you ITB handy work. Thankyou
    #13
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  14. Wiz (J.C)

    Wiz (J.C) Adventurer

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    There's not much to say here. I was on a ride and my engine let go, got it home on the trailer today and found out my intake cam shaft broke. See photo. Will be opening up the rest of the engine to look for any further damage. Thinking the valves and Pistons are toast.
    0914211657.jpg
    #14
  15. Jim K in PA

    Jim K in PA Long timer Supporter

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    That's an odd failure. Did either section of the cam seize in the bearings?
    #15
  16. Wiz (J.C)

    Wiz (J.C) Adventurer

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    Nope, bearings were just fine. Assuming it was an imperfection I'm the cam or a warped head or something
    #16
  17. Wiz (J.C)

    Wiz (J.C) Adventurer

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    After a somewhat late night of disassembly, the doctors prognosis is not good. The work that would need to be done to the head and block to repair this is not worth my time or money.

    That being said, since I am replacing my motor completely, im going to follow in the footsteps of TwoWheelsBetter over at the k100 forum, and install a k1200 motor in its place. In addition that will give me some more electronics to play with like the electronic throttle advance and other gizmos.

    Stay tuned for more I suppose.
    #17
  18. 3legs

    3legs Real men ride sidecars Supporter

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    That is the first failure of that kind I ever heard of in either a K100 or K1100 in fact that's the first I've seen that failure in any bike.
    #18
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  19. Hay Ewe

    Hay Ewe Just a Wannabe

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    will be interested to follow this with electronics upgrade.
    Hope you will continue to post here, please
    (or a link to the other forum and your specific project)
    Thanks
    #19
  20. Wiz (J.C)

    Wiz (J.C) Adventurer

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    Some more information on the damage done, and why I decided to replace the whole engine.

    First thing to go, was the intake camshaft, as you all know. Broke right between cylinders 1 and 2, so the intake valves for cylinders 2, 3 and 4 stopped. The only valve that seems to have been damaged is #4, and some small markings on the respective piston.
    0915211432.jpg

    0915211435.jpg

    After taking the head off, I found more alarming news though. Keen eyed among you will notice the scoring on the cylinder walls. This came a quite a surprise to me, since every single cylinder was scored. Some deep enough it could be felt with a finger. I personally replaced all the rings in this engine when I did all the bearings, and the cylinders looked perfect. I honestly do not know why the cylinders look like this now, the rings were all gapped properly, lubricated when installed, and the bike has always had good oil pressure, so it's somewhat of a mystery to me. The engine was broken in with dino oil for 100 miles and then switched to synth, where there were another 100 miles before the cam failed.

    0915211431.jpg

    In any event, since I was not comfortable leaving the cylinders looking like that, I decided I would replace the engine completely. I felt that the bike was, on the slow side anyway, so I elected to buy a good used k1200rs engine with 60k miles that should put me at 130hp at the crank or more, depending on my tuning. They seem to go for less than k100 engines anyway, and the process to fit it to a k100 trans is fairly simple. Today I spent a good few hours tearing the bike back down again, to get ready for when the new engine is ready to be picked up. Engine was purchased with throttle bodies and fuel rail, to make my life easier.

    Bike ready for heart transplant....
    0916211531_HDR.jpg

    And the new heart....

    Screenshot_20210916-181116~2.png

    Hopefully there will be minimal down time for this transplant, not too much to change on the electrical side, nor the mechanical side, so here's hoping.

    Wiz
    #20
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