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1Back to top Go down    Can Anybody Explain? on Mon Dec 12, 2016 7:40 am

Kafflut

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I have a difficult to start problem I'm trying to figure out [K100, 1986 about 90 000km]

The engine will fire up on about the 3rd go and immediately stop again. On one occasion I accidentally held the starter switch down after that initial couple of revs and the engine kept running. I then released the starter and it continued, a bit rough but it ran.

I repeated this starter hold down on several occasions after that - it seems the only way to get the engine to run.

When the motor starts running and I release the starter switch the revs go lower and lower and it will stall, but if I press the starter the revs pick up and it runs again for a while. This increase in revs happens without throttle or fast idle adjustment, just press the starter switch and it runs faster.

Shocked At this stage I'm certain of one thing only - this holding down the starter and pressing it again when the motor is running is not recommended procedure.

I have an idea this has something to do with another issue I have; once the engine has warmed up it will idle okay but for an occasional miss. Maybe about 3 times a minute it misses - when that happens the instrument lights, the neutral light, ABS etc, all go off for that split second. I put a timing light on the spark plug lead and the timing light also misses. It's like turning the emergency switch off for millisecond and back on again - no electricity for a split second. Can't say it doesn't happen at higher revs; maybe it does but one would not be able to tell.

I have a feeling if I held down the starter all the time the occasional miss will be gone, but since I have no idea what damage I'm doing with this not-recommended action, I'm not going to try it.

Here's what I've eliminated so far: I cleaned battery terminals, cleaned earth connection points, checked coils, cleaned alternator connector, bypassed emergency switch and ignition switch, checked all fuses - I can't remember if I cleaned the fuse connections.

I cannot imagine it not being an electrical fault, but who knows?

I'm ready to try any suggestion - Just don't say 'take it to a dealer' What a Face I did and was told, very old bike nobody in the workshop with knowledge.

I'm hoping that to those with electrical knowledge this starter hold down may be a significant indicator of what's up.

http://bmwk100k75.weebly.com/
    

2Back to top Go down    Re: Can Anybody Explain? on Mon Dec 12, 2016 8:09 am

robmack

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You haven't cleaned the starter moter (not in your list) so that might be a cause.

Pressing the start button while the engine is running tells the ICU to enrichen the mixture, which could account for the increase in engine idle speed. This sounds like the mixture is normally lean and that you should be double-checking for air leaks in the intake system.


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1987 K75 @k75retro.blogspot.ca
2011 Moto Guzzi V7 Racer
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3Back to top Go down    Re: Can Anybody Explain? on Mon Dec 12, 2016 10:02 am

Kafflut

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@robmack wrote:You haven't cleaned the starter moter (not in your list) so that might be a cause.

Pressing the start button while the engine is running tells the ICU to enrichen the mixture, which could account for the increase in engine idle speed. This sounds like the mixture is normally lean and that you should be double-checking for air leaks in the intake system.
Robert,

THAT makes a lot of sense. LOL even to me it does. Thank you much.

But, when I open the throttle or fast idle lever it WILL not start. Is that because throttle/fast idle increases both fuel and air?

I've replaced all the rubber between plenum and manifold and checked with spray can while engine runs and did not find leaks. What I did not check was the crank breather connection - could be some air is entering that way.

When you say "clean the starter motor" do you mean electrical contact points at the starter, and how is that significant?

First on the to-do list, I'm going to look for air leaks again.

Thank you very much for your input. Please keep your eye on this thread - I'll probably have some more questions.

Or ... would it not be great if I can report success affraid

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4Back to top Go down    Re: Can Anybody Explain? on Mon Dec 12, 2016 10:41 am

Point-Seven-five

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Is it possible that your fuel pump only runs when the starter button is pushed?

I don't know how to test it, maybe someone with better knowledge can suggest something.


__________________________________________________
Present:
1994 K75RT
1994 K75S
1992 K100RS

Past:
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

5Back to top Go down    Re: Can Anybody Explain? on Mon Dec 12, 2016 12:10 pm

BobT

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The fast idle lever does the same as holding the throttle open a bit and no more than that.
Cleaning the inside of the starter motor around the brush are seems to cure all sorts of things on a K, and not a difficult job.

    

6Back to top Go down    Re: Can Anybody Explain? on Mon Dec 12, 2016 11:23 pm

Kafflut

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Posting about success may be tempting fate. So for now, I'll talk about apparent progress that needs to be verified later today.

Thanks to robmack, Point-Seven-Five and RobT, it looks like the reason for the difficult start problem has been located Very Happy

I removed the crank case breather tube from the plenum, shoved a plug in there to prevent air from entering the plenum through it. Seems to start just fine now. So I'll be replacing that little tube today and hoping to confirm that the problem is fixed.

Thank you again.

It's still missing a beat several times a minute so I'll be cleaning the starter motor and hope that is as successful.

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7Back to top Go down    Re: Can Anybody Explain? on Tue Dec 13, 2016 12:14 am

Point-Seven-five

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Ah, the dreaded leaky breather hose. Here's hoping that is the problem. Might be a good idea to do a real good inspection of the other rubber stuff around the engine as well.


__________________________________________________
Present:
1994 K75RT
1994 K75S
1992 K100RS

Past:
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

8Back to top Go down    Re: Can Anybody Explain? on Tue Dec 13, 2016 12:57 am

Holister

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@Kafflut wrote:....

It's still missing a beat several times a minute so I'll be cleaning the starter motor and hope that is as successful.
Check your HT leads and spark plugs and connections but sounds to me like you might have a plug starting to fail.


__________________________________________________
1988 K100RT VIN No. 0094680
1989 K100RT VIN No. 0097367 (naked)
1996 K1100RS VIN No. 0451808
Fuel: 95 Octane
Engine Oil:Nulon Full Synthetic 15W50
Gear Box Oil: Nulon Synthetic 75W90
    

9Back to top Go down    Re: Can Anybody Explain? on Tue Dec 13, 2016 1:58 pm

Kafflut

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First, thanks to all for your comments.


Update

I tried it this morning and the engine ran on the third try and did not stall - not bad. I wanted to have one more cold start before ticking the box. I set the air bypass screws, the 4 on the TBs and the one on the AFM to what I consider to be a basic setting. The TB bypass screws I turned in to lightly seated and backed each out one turn. The AFM bypass I closed and backed it out 3 full turns.

I thought that's close to basic setting - I'll balance the TBs later.

I let it stand till early evening - about 9 hours and figured that's a "cold start" It fired up first time. Tick the box. There's still that very slight stumble every now and then.

I'll now do a permanent job on the crank case breather tube and follow the other suggestions, clean starter, new plugs etc

Thank you again.

http://bmwk100k75.weebly.com/
    

10Back to top Go down    Re: Can Anybody Explain? on Tue Dec 13, 2016 2:48 pm

Motorbike Mike

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I hate to bring this up at this late stage but what's the condition of fuel pump like, have you tried a new pump?
I'm thinking that low fuel pressure may lead to similar symptoms, just a thought-sorry!

    

11Back to top Go down    Re: Can Anybody Explain? on Tue Dec 13, 2016 3:19 pm

Kafflut

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Mike, I swapped fuel pumps. Measured the pressure at the rail just to be absolutely sure - it was just below 40psi

I'll do new spark plugs first. I will eventually test the spark plug leads, but I think they're okay. I tested them for conductivity and did a good clean to make reasonably sure I don't have my spark leak down to the chassis before it gets to the plug.

I also connected my timing light to each lead in turn and made sure it flashes on each one of them. I think I mentioned it in an earlier post - during that split second when the engine misses a beat and the instrument lights go off the timing light will also miss a flash.

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12Back to top Go down    Re: Can Anybody Explain? on Tue Dec 13, 2016 4:16 pm

Motorbike Mike

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After reading all you've tried, the pump was the only thing I'd not seen mentioned.

Good luck.

    

13Back to top Go down    Re: Can Anybody Explain? on Tue Dec 13, 2016 6:54 pm

K75cster

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If you are loosing power to everything for that split second, then it must be either the Ignition switch the Kill switch or the relays in the loop. That whole mini event sound electrical. It has two sides, power and earth part of the earth is through the starter oddly enough. Have you cleaned the commutater and checked the brushes.


__________________________________________________
Keith - 1987 K75c with r100rt replica fairing and half of a 1984 K100rt 1992 K1100LT a blue one

The Clever are adept at extricating themselves from situations that the wise would have avoided from the outset - QUOTE from david Hillel in Out of the Earth.
    

14Back to top Go down    Re: Can Anybody Explain? on Wed Dec 14, 2016 12:53 am

Kafflut

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@K75cster wrote:If you are loosing power to everything for that split second, then it must be either the Ignition switch the Kill switch or the relays in the loop. That whole mini event sound electrical. It has two sides, power and earth part of the earth is through the starter oddly enough. Have you cleaned the commutater and checked the brushes.

That's what I'll do then. I have bypassed ignition switch and the kill switch and the hiccup, the split second power out, persists. I will take out the starter and give stuff a good clean - specifically check you the commutator.

Thanks for your suggestions. I'll take a look at wiring diagram and try figure your comment "or the relays in the loop" I'll come back here and ask if I can't work it out.

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15Back to top Go down    Re: Can Anybody Explain? on Wed Dec 14, 2016 6:09 am

RicK G

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Have you cleaned the ignition switch contacts they are well known for intermittent trouble.


__________________________________________________
"Every normal man must be tempted, at times, to spit upon his hands, hoist the black flag, and begin slitting throats." from Mencken's 1919 Prejudices

Bikes 1993 K1100 LT, 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 for now
    

16Back to top Go down    Re: Can Anybody Explain? on Wed Dec 14, 2016 3:04 pm

Kafflut

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@RicK G wrote:Have you cleaned the ignition switch contacts they are well known for intermittent trouble.

Rick, I've replaced the OEM starter switch and emergency(kill) switch. I've also bypassed the ignition switch. That made no difference.

On the difficult start problem ... I've had 3 first turn starts on "cold" since I plugged the breather hole in the plenum. I wanted to be sure before going further. A first turn start on "warm" to me isn't confirmation enough - bike has to stand overnight or for 10 hours.

Next job, replace the crank case breather tube.

On the miss fire/stumble problem ... I'll clean starter motor. If that does not fix the little miss fire/ stumble, then I'll see if I can swap out the relays. After that I'll just live with it - if the fault eventually becomes solid I can track it down.

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17Back to top Go down    Re: Can Anybody Explain? on Wed Dec 14, 2016 7:15 pm

Holister

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@Kafflut wrote:
@RicK G wrote:Have you cleaned the ignition switch contacts they are well known for intermittent trouble.

Rick, I've replaced the OEM starter switch and emergency(kill) switch. I've also bypassed the ignition switch. That made no difference.
There are 3 circuits going thru that switch. How did you bypass it?
.......

On the miss fire/stumble problem ... I'll clean starter motor. If that does not fix the little miss fire/ stumble, then I'll see if I can swap out the relays. After that I'll just live with it - if the fault eventually becomes solid I can track it down.
If this doesn't work, try checking your HT leads, spark plugs and their connections. Sounds to me like you might have a plug starting to fail or maybe an intermittent short to earth. Some dielectric grease on the SP ceramic parts may help.


__________________________________________________
1988 K100RT VIN No. 0094680
1989 K100RT VIN No. 0097367 (naked)
1996 K1100RS VIN No. 0451808
Fuel: 95 Octane
Engine Oil:Nulon Full Synthetic 15W50
Gear Box Oil: Nulon Synthetic 75W90
    

18Back to top Go down    Re: Can Anybody Explain? on Thu Dec 15, 2016 5:45 am

Kafflut

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@Holister wrote:
@Kafflut wrote:
@RicK G wrote:Have you cleaned the ignition switch contacts they are well known for intermittent trouble.

Rick, I've replaced the OEM starter switch and emergency(kill) switch. I've also bypassed the ignition switch. That made no difference.
There are 3 circuits going thru that switch. How did you bypass it?
.......

On the miss fire/stumble problem ... I'll clean starter motor. If that does not fix the little miss fire/ stumble, then I'll see if I can swap out the relays. After that I'll just live with it - if the fault eventually becomes solid I can track it down.
If this doesn't work, try checking your HT leads, spark plugs and their connections. Sounds to me like you might have a plug starting to fail or maybe an intermittent short to earth. Some dielectric grease on the SP ceramic parts may help.
Thanks Holister. This is an opportunity for me to write down my thinking and what I have done and in the process re-assess. I'd value your input regarding assumptions I made and also any suggestions.

How did I bypass the ignition switch? Lifted the tank. Unplugged the ignition switch cable from the rest of the harness. This takes the ignition switch out of the circuit and exposes the pins(maybe sockets-I forget) on the harness side of that connector. I then connected pins to simulate the ON state of the ignition switch.

Clymer(C) and Haynes(H) wiring diagrams differ from the wiring diagram in the Troubleshooting document(T) on the forum. C & H indicate all 4 wires connect to one another in the ON state while T shows RT connected to GN and GR/BL connected to GR. I don't recall which wiring diagram I followed. What would be the difference connecting the C and H ways and connecting the T way?

The way I connected it did not produce smoke Very Happy

Like I said, it made no difference; the fault persisted. I replaced the "kill" switch. Permanently. I'm fairly certain it is not the ignition switch and it is not the kill switch.

How I see the fault:

1.The engine misses a beat about 3 times per minute at around 1000rpm. I don't notice it at above 1500rpm. It may still occur and just be that it's not noticeable at higher revs. Combustion does not happen - let's call it a miss-fire.

2. At the same time as the miss-fire the neutral light and the ABS light go off or at least very much dimmer than during normal 1000rpm running. It appears that the control light flicker happens at the same time as the miss-fire; one can't tell if it's slightly before, exactly at the same time or a millisecond after. But definitely they happen together, lights flicker every time the engine misses.

Assumptions:

1. Fuel availability is not the cause. I changed fuel pump and I measured fuel pressure at the rail - 40 psi - and the fault persists.

2. It seems to be an electrical malfunction

Things I've done and conclusions:

1. I tested the resistance of the coil windings as recommended in the Troubleshooting document by Bertrand Vogel and which is often referred to in the forum. I found the readings to be within the values mentioned there.

2. Ignition switch and kill switch stuff mentioned already.

3 Thoroughly cleaned spark plug leads & connectors as well as major earth points in the wiring.

4. I put an induction timing light on each of the spark plug leads in turn. At the miss-fire the timing light also misses a flash. On each of the plug wires I noticed this. I concluded that it's probably an electrical fault in the system before the coils, intermittent failure in all 4 spark plug leads seems unlikely, spark plug failure ditto plus the pulse does not even happen.

5. I changed spark plugs. I did not renew - I just replaced with 4 plugs that were clean and looked okay. I figured to have 8 spark plugs fail intermittently is unlikely. I temporarily swapped HT leads with another set of HT leads - no change.

6. I checked air temperature & coolant temperature sensor resistance and found it to be within the values recommended in the Troubleshooting document.

Looking ahead:

1. I've already had feedback to clean starter motor commutator, brushes etc. I'll do that.

2. Renew spark plugs

3. Follow any other suggestions members may have for me.

4. Just live with it - if the fault becomes solid one day, ie the motor don't run, I may be able to trace it

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19Back to top Go down    Re: Can Anybody Explain? on Thu Dec 15, 2016 6:37 am

RicK G

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It is not going to be the starter brushes not giving an earth to the load shed relay because the ignition does not draw power from that circuit or they would not start.
I would be checking the harness for a chaffed wire, you may even need to cut the harness open.
Try bypassing the power feed wire with a new piece of wire just a temp thing and same for the negative wire from the coils to the ignition control unit.


__________________________________________________
"Every normal man must be tempted, at times, to spit upon his hands, hoist the black flag, and begin slitting throats." from Mencken's 1919 Prejudices

Bikes 1993 K1100 LT, 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 for now
    

20Back to top Go down    Re: Can Anybody Explain? on Thu Dec 15, 2016 7:18 am

Motorbike Mike

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@RicK G wrote:It is not going to be the starter brushes not giving an earth to the load shed relay because the ignition does not draw power from that circuit or they would not start.
I would be checking the harness for a chaffed wire, you may even need to cut the harness open.
Try bypassing the power feed wire with a new piece of wire just a temp thing and same for the negative wire from the coils to the ignition control unit.
Rick,
That may be a good possibility of a broken wire. I had quite a bit of bother on my Cobas bike, it would cut out for no apparent reason but if I turned it off and on again it fired right up until it did it again. I went through the whole fuel/ignition loom (16v loom on my 8v motor) with a fine tooth comb, testing continuity of every wire but never found the issue. I never found the faulty wire so ended up changing the loom-problem solved.
Even if it's an 8v bike it's a good pointer towards a potential faulty wire that will more than likely get worse.

Again good luck.

    

21Back to top Go down    Re: Can Anybody Explain? on Thu Dec 15, 2016 8:00 am

Laitch

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You seem to be diligent in testing all components of the system, Kafflut. Before you breech the wiring harness perhaps you could substitute a different ignition control unit to determine if that is the source of this symptom.


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1995 K75T 68,000 miles
    

22Back to top Go down    Re: Can Anybody Explain? on Thu Dec 15, 2016 8:10 am

92KK 84WW Olaf

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@Laitch wrote:You seem to be diligent in testing all components of the system, Kafflut. Before you breech the wiring harness perhaps you could substitute a different ignition control unit to determine if that is the source of this symptom.

I would also recommend that too.


__________________________________________________
1992 K100LT 0193214 Alaska Blue 101,000 miles
1984 K100RT 0022575 Baja Red bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Mystic Red 58,645 now 73,300 miles
    

23Back to top Go down    Re: Can Anybody Explain? on Fri Dec 16, 2016 12:27 am

Kafflut

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@92KK 84WW Olaf wrote:
@Laitch wrote:You seem to be diligent in testing all components of the system, Kafflut. Before you breech the wiring harness perhaps you could substitute a different ignition control unit to determine if that is the source of this symptom.

I would also recommend that too.

Been there done that. I also swapped out EFI, fuel injectors, AFM, coils, HT leads.

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24Back to top Go down    Re: Can Anybody Explain? on Fri Dec 16, 2016 12:37 am

Kafflut

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@RicK G wrote:It is not going to be the starter brushes not giving an earth to the load shed relay because the ignition does not draw power from that circuit or they would not start.
I would be checking the harness for a chaffed wire, you may even need to cut the harness open.
Try bypassing the power feed wire with a new piece of wire just a temp thing and same for the negative wire from the coils to the ignition control unit.

Okidoki Rick, thanks I'll be trying that temporary wire from ICU to coils. I've already done the power feed wire you suggested.

Like I said before, if it's in the harness somewhere it's just going to stay there till it's a solid fault and I have to trailer the bike home and find and fix it.

I guess I'd better stop now - Avoid the possibility of Fix it till it's FUBAR What a Face

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25Back to top Go down    Re: Can Anybody Explain? on Fri Dec 16, 2016 9:21 am

Laitch

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@Kafflut wrote:Been there done that.
Enjoy the tour!


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26Back to top Go down    Re: Can Anybody Explain? on Fri Dec 16, 2016 10:07 am

RicK G

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@Kafflut wrote:
@RicK G wrote:It is not going to be the starter brushes not giving an earth to the load shed relay because the ignition does not draw power from that circuit or they would not start.
I would be checking the harness for a chaffed wire, you may even need to cut the harness open.
Try bypassing the power feed wire with a new piece of wire just a temp thing and same for the negative wire from the coils to the ignition control unit.

Okidoki Rick, thanks I'll be trying that temporary wire from ICU to coils. I've already done the power feed wire you suggested.

Like I said before, if it's in the harness somewhere it's just going to stay there till it's a solid fault and I have to trailer the bike home and find and fix it.

I guess I'd better stop now - Avoid the possibility of Fix it till it's FUBAR What a Face
Yep know just what you mean. If you do solve the problem with a temp bypass make it more permanent with some white black zip ties


__________________________________________________
"Every normal man must be tempted, at times, to spit upon his hands, hoist the black flag, and begin slitting throats." from Mencken's 1919 Prejudices

Bikes 1993 K1100 LT, 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 for now
    

27Back to top Go down    Re: Can Anybody Explain? on Mon Jan 16, 2017 1:19 am

Kafflut

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1.The engine misses a beat about 3 times per minute at around 1000rpm. I don't notice it at above 1500rpm. It may still occur and just be that it's not noticeable at higher revs. Combustion does not happen - let's call it a miss-fire.

2. At the same time as the miss-fire the neutral light and the ABS light go off or at least very much dimmer than during normal 1000rpm running. It appears that the control light flicker happens at the same time as the miss-fire; one can't tell if it's slightly before, exactly at the same time or a millisecond after. But definitely they happen together, lights flicker every time the engine misses.

I went for a ride and 5k from home the engine stopped a moment and started again. It did this a few times. I turned and managed to ride back home - slipping the clutch seemed to help keep engine running What a Face

I unplugged the clutch switch. The problem has not happened again.

Question: Can a faulty clutch switch cause the "missing" I've described?

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28Back to top Go down    Re: Can Anybody Explain? on Mon Jan 16, 2017 2:26 am

RicK G

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Yes in theory it could do that if the yellow wire on the switch that connects to the green/black wire was shorting momentarily to earth then the power would be cut to the fuel injection relay and the coils. It's unlikely to happen and not blow the fuse but if it was a very quick touch to earth it could happen.
I would leave the switch disconnected and see how it goes for a week or so then reconnect it and see if it starts happening again.


__________________________________________________
"Every normal man must be tempted, at times, to spit upon his hands, hoist the black flag, and begin slitting throats." from Mencken's 1919 Prejudices

Bikes 1993 K1100 LT, 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 for now
    

29Back to top Go down    Re: Can Anybody Explain? on Tue Jan 24, 2017 11:04 pm

nods

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Looking forward to hearing of a successful outcome!


__________________________________________________
Chassis number0025951
Vehicle code0504
SeriesK589
ModelK 100 RT 84 (0504 ( 0505 )
Body typeK 100 RT 84 (0504
Catalog modelECE
Production date1985 / 01
Engine0514)
Transmission
Steering
CatalyzerNONE
    

30Back to top Go down    Re: Can Anybody Explain? on Wed Jan 25, 2017 11:14 pm

Kafflut

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I did as Rick suggested, reconnected the switch. I could find zip wrong with the switch anyway. The problem turned out to be a nearly invisible bit of exposed copper in that wire! Literally a strand or two of copper showing. I don't think it is a chafe mark, more like someone had touched the wire with a soldering iron.

The clue was the lights going off when I pulled the clutch. Rather sometimes the lights went off when I pulled the clutch. I followed the clutch cable and inspected the wires touching it - that's when I found where the insulation had been damaged. It seems that as the clutch cable moved when under tension it pushed the exposed bit of copper against the frame. The paint on the frame in that area was scratchy - I assume this would mean that sometimes there would be a short.

I taped that wire and I've had two trouble free runs.

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31Back to top Go down    Re: Can Anybody Explain? on Thu Jan 26, 2017 1:47 am

RicK G

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Good to find that you have had success, it's been a long saga.


__________________________________________________
"Every normal man must be tempted, at times, to spit upon his hands, hoist the black flag, and begin slitting throats." from Mencken's 1919 Prejudices

Bikes 1993 K1100 LT, 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 for now
    

32Back to top Go down    Re: Can Anybody Explain? on Thu Jan 26, 2017 2:12 am

brickrider2

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Amazing!

    

33Back to top Go down    Re: Can Anybody Explain? on Thu Jan 26, 2017 6:11 am

nods

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Nice work! That was a hard gremlin to find, but the folks on here led you in the right direction cheers


__________________________________________________
Chassis number0025951
Vehicle code0504
SeriesK589
ModelK 100 RT 84 (0504 ( 0505 )
Body typeK 100 RT 84 (0504
Catalog modelECE
Production date1985 / 01
Engine0514)
Transmission
Steering
CatalyzerNONE
    

34Back to top Go down    Re: Can Anybody Explain? on Thu Jan 26, 2017 6:24 am

92KK 84WW Olaf

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There are a few threads around the forum of the clutch cable movement creating an issue but it's usually becausethe movement isaffecting a less than tight connection somewhere.

That's another one for the checklist when the tank is off.......have a look at the clutch cable movement and maybe a cable tie or two might be needed. Black ones work best.


__________________________________________________
1992 K100LT 0193214 Alaska Blue 101,000 miles
1984 K100RT 0022575 Baja Red bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Mystic Red 58,645 now 73,300 miles
    

35Back to top Go down    Does anyone know ... on Sun Mar 26, 2017 6:09 am

Kafflut

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On K100, when the throttle is closed IE motor idling, is the amount of fuel determined by the AFM or does the EFI say, wait a bit, the Throttle Position Switch is closed, let's deliver a standard volume of fuel(some sort of default)?

By TPS I mean that switch that sits at the rear end of the TBs Very Happy and clicks according what I've read here, but my ears are bad - I have to use a multimeter.

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36Back to top Go down    Re: Can Anybody Explain? on Sun Mar 26, 2017 6:30 am

charlie99

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yes you are right ... the ignition computer sends pulse signals relating to revs (and possibly more ) to the efi computer under seat where some more magic happens with all the feedback signals fed to that computer ..ie afm signals,air temp and flap position , water temp and the tps


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37Back to top Go down    Re: Can Anybody Explain? on Sun Mar 26, 2017 9:24 am

RicK G

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AFAIK the L Jetronic just gives a preset amount of fuel for idle and it only varies according to engine temperature.


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38Back to top Go down    Re: Can Anybody Explain? on Sun Apr 02, 2017 11:00 am

Kafflut

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@RicK G wrote:AFAIK the L Jetronic just gives a preset amount of fuel for idle and it only varies according to engine temperature.

Rick does it "know" to supply this preset amount of fuel (the engine is idling) from TPS input - ie the TPS switch indicating throttle is close ?

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39Back to top Go down    Re: Can Anybody Explain? on Sun Apr 02, 2017 11:28 am

Point-Seven-five

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I believe that TPS just tells the Jetronic that the throttle is closed at high rpm which STOPS injection and thus, backfiring.

The idle injection is triggered by the flapper door in the Mass Air Flow sensor being closed.


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40Back to top Go down    Re: Can Anybody Explain? on Sun Apr 02, 2017 12:23 pm

charlie99

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to be more concise the tps is just an indication to the efi computer that the throttles are closed (or wot , wide open throttle )

there are a few algorithms built into the electronics regarding the tps switch and the wiper from the afm ...and revs

if the throttles are closed and the afm is open and the revs come down to hit 2000 or so ,,then the engine must be braking

so in most cases the injection is stopped until idle revs are achieved ...gives added braking power and a requirement for efi systems to be efficient and not bleed out unwanted fuel ...more to do with epa pollution laws at the time

standard fuel injection returns as idle revs are achieved

there is a bypass built into the afm which signals the efi computer ...the bypass affects the amount of deflection of the afm flap at idle revs so you can adjust //slightly the idle mixture injection algorithm

hope that helps


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41Back to top Go down    Re: Can Anybody Explain? on Mon Apr 03, 2017 9:34 am

Kafflut

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Thanks, Charlie, that helps a stack. My tps does not work. Based on what you say, I'm not going to bust a gut to get a replacement. The engine idles nicely without it and slows down pretty quick when I close the throttle.

Thanks again

In another thread I asked, is the cam shaft thrust washer not a wear part? The book says replace the cam shaft if there's excessive end play - sounds a bit radical. I want to explore rattly engine at low revs and cam end float is stated as a possible.

I suspect the actual cause is wear in the timing chain, guides etc and it causes lurching, for want of a better word, of that mechanism at low revs. Over 1500 rpm it runs nicely.

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42Back to top Go down    Re: Can Anybody Explain? on Mon Apr 03, 2017 9:39 am

Laitch

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@Kafflut wrote:
I suspect the actual cause is wear in the timing chain, guides etc and it causes lurching, for want of a better word, of that mechanism at low revs. Over 1500 rpm it runs nicely.
These engines will rattle like hell if they aren't given enough revs at takeoff and at gear changes. Post the sound file will help with clarity.


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43Back to top Go down    Re: Can Anybody Explain? on Mon Apr 03, 2017 10:00 am

charlie99

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lurching sounds more a mixture issue ...and are quite noticeable in a cyclic nature
a couple of possibilitys could be perhaps

leaks in throttle body rubbers

a worn out afm resistor - wiper connection (happens at the low end of its range )

if you could borrow an afm off someone I would be trying that as I think remember you doing something with the rubbers to the head ?

but I'm not clear on that

just a suggestion


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44Back to top Go down    Re: Can Anybody Explain? on Mon Apr 03, 2017 11:57 am

Kafflut

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Thanks, Charlie & Laitch

I was hesitant about using the word "lurch". Uneven running due to slack in the chain would be a better way of describing it. With a slack chain at low revs one could expect that the slack would be taken up, then there may be a bit of overrun and loss of tension in the chain, then the slack is taken up again and so on. Then when increasing revs, the chain is under tension all the time and the noise goes away. Anyway, it's a theory. But I'll make a recording and try post it.

I hear what you say about these engines being noisy if you don't keep the revs up - it makes sense.

I replaced all the rubbers, TBs are balanced, valve clearance okay, compression okay. I'm happy with the running. I'm going to open it and check the timing chain mechanism to see what I can see. The reason for talking about it is that I'll be checking cam shaft end float and if I find too much end float I'd like to have a plan. The manual says replace the cam shaft. A not-renewable thrust bearing on the cam shaft sounds not-clever to me.

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45Back to top Go down    Re: Can Anybody Explain? on Mon Apr 03, 2017 11:59 am

Kafflut

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Oh yes, the AFM I have access to another one. I did swap out AFM a while ago and detected no difference, but it's a good idea to do it again because I've made some other changes since.

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