hey,

i changed the rubbers connecting the throttle bodies with the airfilter the other day (yeah yeah, i know, where are the pics and instructions... i charged my battery and forgot to take the camera with me to my friend's garage...) and what came out is that one of the throttle bodies (2nd from the front) was completely black inside (wet black, like unburned oil). the valve clearances is ok, the timing chain is ok (we changed that too) and all seems ok. do you have any ideas what can it be? valve bed burned? except that the bike runs normal. should i worry?

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

thanks charlie! it looks like a job for someone who has a heated garage and has no employment (but a lot of savings) so he can sit down and spin those bolts for days )) well, i should've checked it all when i had the air filter off and everything but yeah, i would also bet on 1) intake valve seat or/and 2) valve stem seals... the spark plug looks ok though, same as the rest. the rough running didn't go away as i thought it will after changing the rubbers and checikng for air leaks but when the temperature is above 5 degrees C the engine starts fine when cold and makes no weird sounds. when it's colder though it knocks a bit at the beginning (maybe temp sensors?)

also, the thing i wrote about earlier keeps me a bit stressed as it gets louder with time. when i go to work in the mornings and it's cold (2-5 degrees C) and i rev the bike up to 3-4k rpm and brake with the engine i can hear a loud rattling (the dry rattling). it's definately not the alternator so maybe this spring on the shaft someone told me about earlier but this all would need the engine taken off to check.

i am just asking if i should forget about it for now or should i definately stop riding it and fix it all first?

thanks again,

PS i guess i should finally post some pics of my brick haha will do soon

the rattling could be the output shaft coupling .......and if the engine was running unevenly ..that might explain a more pronounced noise

gee ive forgotten if yours was an early model with the 6 rivett output shaft coupling ...please forgive me ...

hell i wouldnt stop riding .....but...it would certainly be better if the old girl was running sweet ....no ?

i have to do all the bearing and seals throught on my old gal too ...hopefully next year i can get down to it properly ...and replace all those things ...gearbox included ...(thanks alby ) and lessen the overall noise of sloppy parts .....

but i cant just yet .....i must have a bug ...and can't stop riding ...cheezy grin

as the engine warms up ...the viscosity of the oil drops paj ...and more likely to escape past those valve stem seals adding to the problem slightly

gee wiz it would have been hard to notice the black inlet path ...as the throttle boddies have a trumpet inside the plenum (for torque management - manipulation accross all revs i suspect ) which would almost make discovering the carbon impossible ...untill undoing the tbs

yes it will take a while of patience and well thought out refurbishment to make her as good as the day she was born ......but really just some simple things could-should be done in the not too distant future to keep her going ....

you have summer over there mate so of course it would be hard for you to stop riding now

it's getting pretty damn cold over here and if i only had a garage i would dig into those nuts and bolts and change all those damn bearings, rivets etc! mine is a 6 rivet version (99% sure).

well, we'll see, but somehow taking the engine off the bike petrifies me as this construction is sooooo compressed, heavy and tight - it's not a 600 jap bike

no it isnt, but no more complicated ....just heavier ...

[quote]..gearbox included ...(thanks alby )

Your welcome!!!