charlie99
VIP
Number of posts : 11701
hmm ... a simple test would be to do a compression test on all cylinders paj .... others will say that a leak down test is more accurate and rightly so .... but as a quide this could give you some sort of answer
what i would be listening for is air blowing back from the inlet valve of that particular cyliinder ....you may have to bring the crankshaft around up to compresion on that cylinder slowly ....like using the cam shafts to turn the whole thing over with that big spanner attached to the inlet cam ....(caution this may stretch the cam chain a little ,but if the movement is smooth maybe ok to do ...no jerking please and plugs in or compression tester whilst doing this ) and listening for a hiss of presure escaping back out the inlet valve ....if this is found ...more than likely will be that the valve seat has suffered a little over time and needs a valve regrind .. quite often oil or unburnt fuel will settle on the valve lip causing a slight blowby condition ...which over time will eat away at the valve face and seat
if no noise of escaping air can be heard
there are a couple of other possibilities ...being that there might be a slight leak through the head gasket allowing oil to bleed into the combustion chamber ....(durring the normal running there is always a slight blowback effect whilst at speed ) ....especially when decelerating from 3000 revs down to idle and this might be spitting a little oil back up the induction system......but more likely that if there has been an issue with missing ignition (spark) before .....and i think you did suffer from this before changing the ignition leads ???
it may be the fact that it has been running rough previously ....it would take some time to clear out the black carbon effect of the inlet path if at all except for manual cleaning ...
but more likely that the valve stem seals could be cracked ....and needs replacement .(another cause of oil leaking into the inlet chamber ...and then back out the inlet path -throttle bodies ..(as well as eventually the exhaust path )
i would be betting at best quess that its the valve stem seals on that cylinder ....if your doing just the one that shows the black soot ...i would be concidering replacing them all at the same time ..
hope this helps some
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'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
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1987 k100rs ######## "Red" - (red sports rs TWB style )
1989 K100rt #009637 "Black Betty" (naked rt ala Nigel , now sporting an rs main fairing )