BMW K bikes (Bricks)

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robmack


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chris846 wrote:Post #1: "The air flow meter is new me,"


What do you mean by this?
I'm not saying the AFM is defective. I'm saying that the tests might not actually be proving the injector circuitry because of leaks to ground through the way the AFM is connected possibly.

http://k75retro.blogspot.ca/
    

Suzi Q

Suzi Q
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Hi Rob, crossed purposes: the OP described the AFM as ‘new to me’. Not sure if that means it’s an untested unit, or whether the technology is ‘new to me’. ‘Pologies if I’m off track, but the OP’s video shows his bike behaving exactly as it would if the AFM were disconnected - and he’s already mentioned damage to the FI loom....🤔


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Sometimes I'm not really Suzi Quatro.
    

TrailKlaus

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chris846 wrote:Post #1: "The air flow meter is new me,"


What do you mean by this?
What I meant was that yes, the technology is new to me. Most of my other bikes have been carbureted and haven't had any kind of air flow sensor.

    

TrailKlaus

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I reconnected all of the injector harnesses, and I did the "screwdriver test" again, and I am now getting rapid ticking on all injectors when running the starter. 
If there isn't a more likely culprit at this point, I'm definitely keen to look at the AFM as a potential problem here. As I recollect I cut/spliced the wires coming from it into the new harness. It would probably be worthwhile to open up the meter and test continuity to make sure that I spliced the right wires together and didn't short anything.

    

105Back to top Go down   Troubleshooting a 1985 K100 that won't start/stay running - Page 3 Empty a different direction Fri Feb 26, 2021 12:07 pm

Paddy1

Paddy1
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question to the group. 
Is it possible that improper throttle (idle setting) will convince the ecu to shut down?
as this was a very early version of Fuel injection for BMW motorcycles.

+1 daveyson computer stuff way over mine too.


__________________________________________________
Riding Beemers since 1988
1986 K100RT, 1985 K100RS, 2001 K1200LT, 2004 R1100S, 2004 R1150, 1980 R65, 2014 Zero FX
    

Suzi Q

Suzi Q
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Hi Trailkaus - did you look at the video I posted at #84? I can be a bit obtuse, sorry, but the video was basically me disconnecting the AFM on one of my bikes and then starting the engine - that coughing & half running that it does sounds an awful lot like the video you posted of your bike.
If you've had to repair the wiring loom to your AFM, I'd, well......fingers crossed but at least it'll be a cheap repair. Good luck.


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    

TrailKlaus

TrailKlaus
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Just to continue documenting: I pulled the EFI plug and tested continuity there to evaluate the AFM, as described here: https://www.kforum-tech.com/electrical/EFI/bike-wont-start-EN.htm
All of the AFM values appear to be pretty much as expected, with no indication of shorts or crossed wires.

@Chris let me go and take a look at that video

    

robmack

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@Paddy1 wrote:question to the group. 
Is it possible that improper throttle (idle setting) will convince the ecu to shut down?
as this was a very early version of Fuel injection for BMW motorcycles.
No, it won't. An improper idle adjustment will turn the idle switch off, but the engine RPMs will be less than 2000 at idle so the EFI is still in control of the injectors. The idle switch indicates either idle or full throttle. The idle switch in idle position tells the ECU to cut off the injectors on engine deceleration (you suddenly close the throttle while under way) and the injectors remain offline until the RPMs go below 2000 at which point the ECU again takes over control of them.


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Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

Suzi Q

Suzi Q
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+1. The bike will run mostly fine without a TPS at all, or with a wrongly adjusted TPS. It will:

1: pop on the overrun because (as Robmack detailed) not shut off the FI when you shut the throttle quickly above 2000rpm.

2: Less obviously, have a bit of a loss of power/engine dying problem at low/mid-range rpm when the throttle is opened. This occurs rarely, but seems to require a particular combination of revs/engine load/throttle opening to expose this weakness - it's this combination that, I guess, is the reason for the WOT switch on the TPS - to prevent it happening!

I binned the TPS on the Madass, but I had to reintroduce a WOT switch to overcome problem 2 - it was dangerous with sudden acceleration (or not!) in traffic.


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    

caveman

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Good read this thread is!
Nice work guys on the fi relay!
At this point (based on last vid clip), I think your still getting over fueled. Did you check the temp. input to fi ecu. If so (and good) do you have access to known good injectors?

    

cycleman

cycleman
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I have read some BMW bulletins on the early K's where the ECU, Ignition control unit, would get damaged because the case leaked and would allow water to enter. They had a range of serial numbers for US models but nothing for any where else in the world, so I don't know if this would apply to your bike. For the K100 0030001 - 0031222. K100RS  0040001 - 0041954, K100RT 0050001 - 0052267.

They updated the ECU in November 1984, to fix this problem, so I don't think it would apply to your 85, unless it had a 84 yr production date. This was a factory defect and the ECU was to be replaced on all bikes falling into the above serial # range.

I post this for info purposes.

    

Paddy1

Paddy1
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robmack.
thank you for your reply to my question.


__________________________________________________
Riding Beemers since 1988
1986 K100RT, 1985 K100RS, 2001 K1200LT, 2004 R1100S, 2004 R1150, 1980 R65, 2014 Zero FX
    

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