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K100-forum.com » Technical, repair and troubleshooting » Engine and transmission » k100 stumble at 1800rpm

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1Back to top Go down   k100 stumble at 1800rpm Empty k100 stumble at 1800rpm Tue Jul 24, 2012 1:32 am

yankeeone

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Hi, any ideas why my 86 k100 would start to stumble / vibrate at about 1600 to 200 rpm, runs good every where else, did out put shaft, plugs wires ,injectors ,valve adjust ,timing, balanced tb idles nice runs right up to red line, thinking maybe the tps? but I am at a loss, bike gets pretty bad vibs at the same time as rough running.
Thanks

    

2Back to top Go down   k100 stumble at 1800rpm Empty Re: k100 stumble at 1800rpm Tue Jul 24, 2012 10:00 am

Rick G

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Are your plug caps secure, do you have the little bobbins on the plugs or is the thread bare.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1999 K1100 LT with a Big Block 1200
    

3Back to top Go down   k100 stumble at 1800rpm Empty Re: k100 stumble at 1800rpm Tue Jul 24, 2012 10:10 am

yankeeone

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hi , checked the wires and plugs ,yep the bobbins are on, we used the stethoscope and are thinking that maybe it could be bad rod bearing or piston pin. there is a fair amount of noise, right at 1800.

    

4Back to top Go down   k100 stumble at 1800rpm Empty Re: k100 stumble at 1800rpm Tue Jul 24, 2012 10:19 am

Rick G

Rick G
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Have you checked the monkey nutz on the alternator drive they can get real rowdy if they are worn out. The other thing is maybe if you have a 6 rivet shaft the rivets could be losing their grip.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1999 K1100 LT with a Big Block 1200
    

5Back to top Go down   k100 stumble at 1800rpm Empty Re: k100 stumble at 1800rpm Tue Jul 24, 2012 10:41 am

yankeeone

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yep ran it with no alt, and the shaft was updated to 12 rivet.
thanks

    

6Back to top Go down   k100 stumble at 1800rpm Empty Re: k100 stumble at 1800rpm Tue Jul 24, 2012 12:22 pm

charlie99

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could it be lead or coil breakdown ...???

they tend to suffer more noticably when under load in the lower revs .

results could give apparent missfires and that bottom end type knock effect .


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
1987 k100rs ########   "Red"  - (red sports rs TWB style )
1989 K100rt #009637   "Black Betty"  (naked rt ala Nigel , now sporting an rs main fairing )
    

7Back to top Go down   k100 stumble at 1800rpm Empty Re: k100 stumble at 1800rpm Wed Jul 25, 2012 2:07 am

yankeeone

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is it possible the hall sensor is bad? is there a way to test it? the thing starts right up, but breaks up ,runs rough at 1800. Wires good from other bike that ran well,

    

8Back to top Go down   k100 stumble at 1800rpm Empty Re: k100 stumble at 1800rpm Wed Jul 25, 2012 4:19 am

yankeeone

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ok switched out hall unit, no change, if I open up the oil fill it seems to exaggerate the problem , but I cant find any vacuum leaks, possable air flow meter?

    

9Back to top Go down   k100 stumble at 1800rpm Empty Re: k100 stumble at 1800rpm Wed Jul 25, 2012 9:54 am

Rick G

Rick G
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I well could be the AFM if the variable resistance is not smooth in its progression


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1999 K1100 LT with a Big Block 1200
    

10Back to top Go down   k100 stumble at 1800rpm Empty Re: k100 stumble at 1800rpm Wed Jul 25, 2012 11:00 pm

yankeeone

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I just went out and tried the bike this morning. I pulled the vacume line from the #4 tb to the fps, not much change but i did see a small flame in the little brass nipple on backfire, so I know at least #4 is backfiring,

    

11Back to top Go down   k100 stumble at 1800rpm Empty Re: k100 stumble at 1800rpm Thu Jul 26, 2012 4:44 am

yankeeone

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hi , compression test - 150 avg. over the four. start it up it, runs fine for thirty seconds or so then it starts to stumble.
checked the spark at the same time, some times yellow , good or bad?

    

12Back to top Go down   k100 stumble at 1800rpm Empty Re: k100 stumble at 1800rpm Thu Jul 26, 2012 5:17 am

yankeeone

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took out air flow sensor and found the flap does not run smooth, can I clean it? does it come apart?

    

13Back to top Go down   k100 stumble at 1800rpm Empty Re: k100 stumble at 1800rpm Thu Jul 26, 2012 7:57 am

twincarb

twincarb
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having being reading about the timing which is one thing you said you have done.... it can depend on where you "tune" it to as to how the vibrations are... it could be that with a slight adjustment you will loose the vibration...


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BMW K100LT 1988 Matt Black Peugeot Electra Blue (ELX) Colour is now confirmed...
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k100 stumble at 1800rpm 169042k100 stumble at 1800rpm 169034
    

14Back to top Go down   k100 stumble at 1800rpm Empty Re: k100 stumble at 1800rpm Thu Jul 26, 2012 8:04 am

charlie99

charlie99
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yes the flap runs on a pivot ....which is spring loaded from one end ....i think the other end is housed in a socket of the assembly (the other side of the air guide ) be carefull if you do anything that might contaminate the air temperature thermistor near the inlet path


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
1987 k100rs ########   "Red"  - (red sports rs TWB style )
1989 K100rt #009637   "Black Betty"  (naked rt ala Nigel , now sporting an rs main fairing )
    

15Back to top Go down   k100 stumble at 1800rpm Empty Re: k100 stumble at 1800rpm Fri Jul 27, 2012 2:48 am

yankeeone

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Platinum member
Platinum member
hi switched out air flow meter, 99% improvement, the flap on the old one was a bit sticky in the just starting to open range. going to try new to me, but good coils to see if that helps the last 1%
thanks

    

16Back to top Go down   k100 stumble at 1800rpm Empty Re: k100 stumble at 1800rpm Sun Aug 05, 2012 11:09 am

yankeeone

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I just opened up the faulty air flow meter, one of the wires had worked itself down to the point it was rubbing on the moving parts, I will put it back in service.

    

17Back to top Go down   k100 stumble at 1800rpm Empty Re: k100 stumble at 1800rpm Sun Aug 05, 2012 11:16 am

Rick G

Rick G
admin
admin
Great news, one more good result.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1999 K1100 LT with a Big Block 1200
    

18Back to top Go down   k100 stumble at 1800rpm Empty Re: k100 stumble at 1800rpm Sun Aug 05, 2012 5:58 pm

charlie99

charlie99
VIP
VIP
+1 ......good investigating ,


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
1987 k100rs ########   "Red"  - (red sports rs TWB style )
1989 K100rt #009637   "Black Betty"  (naked rt ala Nigel , now sporting an rs main fairing )
    

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