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K100-forum.com » Technical, repair and troubleshooting » Engine and transmission » One black spark plug.

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1Back to top Go down   One black spark plug. Empty One black spark plug. Mon May 05, 2014 10:01 pm

enzo

enzo
active member
active member
Changed the spark plugs and one was completely black. The others were the normal light grey.
I than pulled the same cylinder plug again after 200 miles and again it is very black. Not oily but very dry and black.

This is a bike I have had for less than two weeks. 1985 K100RS with 29k on a working ODO. I know the miles are an unknown. No smoke at start up ever and bike seems to run fine. Any ideas?


__________________________________________________
1985 BMW K100RS Alaska Blue
2012 KTM 500 XC-W
    

2Back to top Go down   One black spark plug. Empty Re: One black spark plug. Mon May 05, 2014 10:04 pm

Rick G

Rick G
admin
admin
It sounds to me that the injector may be sticking open. My first move would be to get the injectors serviced.


__________________________________________________
"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   One black spark plug. Empty Re: One black spark plug. Mon May 05, 2014 10:22 pm

kartooo

kartooo
Silver member
Silver member
is it #4 ?
the one that has the vacuum line going to the fuel pressure regulator.
if the membrane in there gets perforated it will suck fuel in by way of the vacuum line.
just like the old vacuum modulators on transmissions. when bad the engine would suck in trans fluid.


__________________________________________________
85 k100rt current
04 vulcan 1500 classic sold
07 bonneville black sold
05 fjr1300 sold
04 r1150rt sold
91 k100lt sold
r80rt sold
85 K100 sold
    

4Back to top Go down   One black spark plug. Empty Re: One black spark plug. Mon May 05, 2014 11:48 pm

enzo

enzo
active member
active member
It's cylinder number two. Good info however!


__________________________________________________
1985 BMW K100RS Alaska Blue
2012 KTM 500 XC-W
    

5Back to top Go down   One black spark plug. Empty Re: One black spark plug. Mon May 05, 2014 11:55 pm

Rick G

Rick G
admin
admin
Try changing #1 and #2 plug about as it could be a bad plug.


__________________________________________________
"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
    

6Back to top Go down   One black spark plug. Empty Re: One black spark plug. Tue May 06, 2014 6:44 am

92KK 84WW Olaf

avatar
Life time member
Life time member
When you fire it up from cold just check and see does the exhaust header heat up as fast on no 2 cylinder. I had a similar issue on the LT, changed plugs and got a dud plug, after a second change all was fine.

If the exhaust is not heating up try swapping the plug leads between 2 and 3 if you can. If it is heating up check out the injector but if not heating up check out that its actually getting a spark.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011157 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 58,200 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 51,800 miles.
1983 K100RS 0004449 Odette R100 colours 58,000 miles. Sprint fairing now 63,390 miles

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

7Back to top Go down   One black spark plug. Empty Re: One black spark plug. Tue May 06, 2014 10:00 am

k75RT Keith

k75RT Keith
Silver member
Silver member
If the plug swap fails, either upgrade to the new style injector and you can send your out to Mr. Injector in Idaho.  Usually turns them around in a day or 2.

    

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