BMW K bikes (Bricks)


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1Back to top Go down   Sooty spsrk plug Empty Sooty spsrk plug Tue Apr 05, 2011 4:33 am

redman

redman
active member
active member
I've noticed that on my 85 K100RS that the #4 spark plug is very sooty compared to the rest. The others all look white. I'm thinking that this is a rich condition possibly caused by incomplete fuel atomization from the injector. Or maybe low compression?

Also of note when trying to solve a rough idle, I sprayed brake kleen on the #4 intake boot. It made no immediate difference but it seemed that the solvent eventually soaked through the intake boot & the engine ran very smooth until all the brake kleen was exhausted.

Thoughts?

    

2Back to top Go down   Sooty spsrk plug Empty Re: Sooty spsrk plug Tue Apr 05, 2011 3:47 pm

charlie99

charlie99
VIP
VIP
hmmm ...kinda sounds like a lot of posts we have seen about the boot rubbers and air leaks .

sooty plug ....could this be lack of full compression (ie valve clearances /seating)
might be a good idea to do a compression test and compare the results (if you have a guage handy )....

the crank case breather tube enters the plenum right above no 4 intake and i wouldnt be surprised to see some gunk buildup sitting in the valve intake area under that stub as well as through the throttle bodies maybe the brake cleaner loosened up some of the crud sitting there in the valve intake area .

im thinking a good cleanup of the area (throttle bodies and rubbers internally) might be a wise idea. new plugs etc ...but dont forget to check your high tension leads ,coils etc



im definatly doing mine as soon as i get a chance ....after new tyres , driveshaft, as so forth..that list keeps getting bigger...lol

    

3Back to top Go down   Sooty spsrk plug Empty Re: Sooty spsrk plug Wed Apr 06, 2011 10:10 am

japuentes

japuentes
Life time member
Life time member
Hi there, sooty how? is it black dry and porous or looks oily?
In the first case (assuming all the electricals are ok) you can have a miss balanced trottle causing a rich mixture, most probably at iddle. If oily then a valve seal, guide or a piston ring.
Best regards
JAP

    

4Back to top Go down   Sooty spsrk plug Empty Re: Sooty spsrk plug Wed Apr 06, 2011 1:11 pm

redman

redman
active member
active member
The plug is dry & much darker than the others. Looks like incomplete combustion to me. I plan on doing a compression test when I have the timing chain back on. I'm wondering about a clogged injector?

    

5Back to top Go down   Sooty spsrk plug Empty Re: Sooty spsrk plug Wed Apr 06, 2011 1:19 pm

japuentes

japuentes
Life time member
Life time member
Regarding incomplete combustión (rich mixture) I agree with you, and it could also be an injector, but had you check TBs synchro at idle?.
I think its easier than messing with the injectors
Best regards
JAP

    

6Back to top Go down   Sooty spsrk plug Empty Re: Sooty spsrk plug Wed Apr 06, 2011 8:44 pm

redman

redman
active member
active member
I have not checked the synchro but intended to do it at some point. I will do the comp. test first because I'll have the tool & when the bike is back together, I'll get a synch tool & check that first.

Thanks!

    

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