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1Back to top Go down   1985 K100RS not running right Empty 1985 K100RS not running right Fri Jun 28, 2013 11:12 pm


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I have a 1985 K100RS that is ailing. It has about 41,100 miles on it and had generally been reliable until one day. To be specific it ran fine one day, and I came home and parked it and the next morning this problem presented itself. It wasn't starting (it was turning over) and gas was dripping out of the union where the headers meet the tailpipe.
Here is what I have done:

Cleaned the electrical connections (not inside of the relay box recently)

I inspected the plugs and it seemed that cylinder #4 was flooding

My spark plug leads were replaced with a new set from Beemer Boneyard about 5,000 miles ago

I gapped and replaced the spark plugs

I visually confirmed that all plugs were sparking

I tested the ignition coils, mine were reading low (coil1/4 9.87k ohms at HT, and 2.9 at the leads. and 2/3 was 9.69k ohms at HT and 3 ohms at the leads). I ordered a used set to replace them. The used set came with 1 good coil and 1 bad coil. Swapping the good coil in resulted in it starting but not firing on all cylinders. I ordered two new OEM coils with orange towers and have installed them.

I measured the fuel pressure (36 pounds as expected)

I checked the resistance on the injectors they varied from 15.8-16.6 ohms

I checked that all the injector leads were pulsing with a 12V LED

I manged to find a set of 4 new injectors for cheaper than the cost of having mine cleaned. Installed them and though it still doesn't idle correctly there is no longer fuel pouring out of the union in the exhaust

I replaced the air filter

I replaced the fuel filter

I replaced all the fuel lines outside of the gas tank as they were old and cracking

I installed quick disconnects on my fuel lines that has made removing / installing my tank a lot more pleasurable

I replaced the alternator drive bushings

I replaced the coolant level hose

I replaced the Z engine breather hose (it was cracked and had foamy goop in it)

I checked for vacuum leaks with a propane cylinder

My battery is reading 13.23 volts

When I last started her up she wouldn't idle without me staying on the throttle and when I let off would pop and die. This seems to be the case whether the Throttle Position Switch is connected or not.

The plugs all look good and not flooded

I can rev the engine up to 8,000 RPM in neutral on the center stand with a bit of hesitation around 2,000 RPM and it seems ok

I placed a penny between the throttle body adjuster screw and stop and it seems to idle now.

When I take it for a test ride it feels like it has no power and isn't running like it was previous to the day when it decided to no longer start.

Could anyone suggest where I should go next before working my way through all the other items in the EFI/Electronic ignition K100 2v troubleshooting guide? I'm really hoping to make it the BMWMOA rally in Salem, but at this rate I don't know that I will. I only have two more paychecks before I need to leave. Thank you!



2Back to top Go down   1985 K100RS not running right Empty Re: 1985 K100RS not running right Sat Jun 29, 2013 12:45 am


That sure is a list.

Welcome to the forum.

Only suggestion I have is check the temp sensor connection. Hiding in behind the radiator.
If it is not connected correctly it will display the non starting issues you mention.

1986 K100RT VIN 0093801K100RT with summer fairing for a northern visitor

Basic/2 6308802K100CJ  05/1988

K1100RS 0194321

3Back to top Go down   1985 K100RS not running right Empty so Sat Jun 29, 2013 1:28 am


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So basically, you have the idle stop propped open way farther than normal to keep it idling and it's not making power on accel.

Is it running smoothly or is it stuttering on accel?.

Could be a lot of items going on here. You have changed a lot of things while trying to correct this. It is possible that another problem was created in error while repairing something. Not sure at this point.

From this point need to be methodical and not change or replace anything else to avoid the possibility of creating a problem while searching for another.

Looking at your post for clues:

#1 the coils are interchangeable....the only things different are the stickers. It appears that you have at least 3 good coils to swap around. And were the originals truly bad? Could maybe try to reinstall those to see if any change. Also need to double check to see that the correct wires are on the correct spades.

#2 Assume the air & fuel filters are ok. Assume the fuel lines are ok, although some kind of problem could have been introduced by installing the disconnects that are not standard. It seems unlikely. (See #12 below)

#3 assume the Alternator work was not related to the problem.

#4 assume the coolant level hose is not creating a problem.

#5 check the new breather hose to be sure nothing got kinked or torn during install.

#6 Insure that the oil fill cap is correct , tight & secure.

#7 Probably be good to R&R the connector plugs at the engine computer and the ignition module just to be sure that they are clean and did seat up correctly. Often times the engine computer plug may not fully connect when re-assembled.
#7A R&R the connector plug at the bottom of the left front of the fuel tank to see that it seats up correctly & snugly.....may need to slightly spread some pins there to get a tighter fit. See other posts about that.

#8 Double check to see that all of the spades on the tan wires of the ground stack got re-attached when cleaning and 1 hasn't fallen aside & been missed.

#9 The problem now sounds Ignition related to me.

#10 Insure that the spark plugs have all the little round nubby tops screwed on them as designed. Be sure all of the big metal spark plug caps are pushed fully home on the plug ends, they go on quite hard. Twist and push with sturdy pliers.

#11 insure that we haven't cracked the porcelain on one of the plugs during the work.

Perhaps the original failure was the #4 injector staying fully open & flooding that cylinder. Some other problem has occurred during the trial & error repairs.

#12 double check that the air filter cartridge went in flat and fully only goes in 1 way up and one way around. Double check the elbow between the air filter box outlet and the air plenum inlet to see if all is correct and no leaks there.

#13 often times, new people might try to disconnect the air elbow from the front of the filter box top when changing the filter. It will not come off from there & can be damaged on that end, creating a leak between the air flow meter & the plenum.

#14 Do another anything else not working correctly.

#15 check power on both sides of all 7 fuses.

You will correct this before Salem.

I'll be leaving from Phoenix on Monday 7/15 toward Salem......I'll bring a tow rope....LOL

I'm sure others will chime in with more ideas

Regards, Ibj...


4Back to top Go down   1985 K100RS not running right Empty Re: 1985 K100RS not running right Sat Jun 29, 2013 1:58 am

RicK G

RicK G
Foamy goop in the crankcase breather hose will come about due to water in the oil but often is only condensation if you havent done any long rides for a few weeks.
Have you checked the cylinder compression, water in the oil or oil in the water I am thinking the head gasket may have been damaged from a small hydraulic on #4 with a heap of fuel in the cylinder.
The not starting initially could be that the fuel in the exhaust was drawn back into the other cylinders at the initial turn over or that it condensed in there overnight.
I would be going through the trouble shooting guide step by step it really is a good guide.
Check the valve clearances to see if any have changed to any marked degree this can often be a good indicator of a problem area.

"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 2004 K1200GT 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki

5Back to top Go down   1985 K100RS not running right Empty Re: 1985 K100RS not running right Sat Jun 29, 2013 2:02 am


measure the plug leads from plug top to other plug top on both the coil pairs

see that you get a reading about 20 k from 1 to 4 and 3 to 2 (plug 4 was black, suspect lead or not mounted into tower properly )

is the tube from the air cleaner box to the plenum fitted up correctly (that big 60-70 mm right angle bend in front of the box ...behind the radiator

or leaking injector on 4

or valve too tight issue ?

just my weird thoughts

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

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O1985 K100RS not running right Au-log10

'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..

6Back to top Go down   1985 K100RS not running right Empty It's alive! Mon Jul 01, 2013 8:10 pm


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active member
Thank you so much everyone who responded, I'm sorry it has taken a little while to get back with a reply. Saturday morning I wrote up a long list of all the suggested places to look and went to work on the bike.

I found two issues that were likely causing my frustrations. The first was that the water temperature sensor wires had not been fully seated from when I cleaned the connection last. The second was that when I received my new coils I managed to swap a plug wire between the 1/4 coil and the 2/3 coil. I discovered this when I was testing the resistance of the plug leads and I found the lengths to be off between cylinders 3 and 4.

So she's back to running, now I just have to put all the fairing pieces back on. Thank you again for all your help! I look forward to seeing some of you in Salem for the BMWMOA rally.


1985 BMW K100RS
1984 Honda Shadow VT500C

Last edited by KiltedK100 on Mon Jul 01, 2013 9:02 pm; edited 1 time in total (Reason for editing : spelling error)


7Back to top Go down   1985 K100RS not running right Empty Fine then! Mon Jul 01, 2013 8:55 pm


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Life time member
OK, I'll leave my tow rope at home!


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