hey everybody....
I have recently been having some noise from engine on the 93 CBR 600. So, i pulled the all apart, and checked the head for valve damage. All the valves and pistons were free from marks or marring. when i put it back together i checked all the valve clearances, and they were all in spec. there was a little wear on the journals at the end of the camshafts near the cam chain sprockets, but no marring or gouging. all the other journals were perfect as were the camshaft lobes.

then, under closer inspection I realized that the cam chain tensioner guide was worn, so i replaced it. i put everything back together.... still had chain noise...

So.. i ordered a new cam chain, pulled the bike apart again and installed it. Buttoned everything back up. now, there is no chain noise, but i seem to have a loud mechanical knock.

I called a buddy over and we ran the bike, and then, in order to hear the noise better we disconnected the coils and ran it on the starter... and now there is no noise... WTF is going on?!

any help would be appreciated. i dont mind pulling the bike apart again but i have no idea what to look for. did i miss something?

I have only run the bike for about 5-10 minutes since i put it back together. the knocking just sounds very bad and i dont want to do any more damage.

my carb boots are tight and my header is tight, so i don't think it is a fuel/air thing, However, when we ran it last night Cylinder no. 3 didn't seem to be firing, though it had been earlier in the day.

one other thing... if the stretched cam chain jumped a tooth, it would have screwed my valves up, but if it had wouldn't that have been apparent when i checked my valve clearances?

and what if it isnt the top-end? what else could it be? maybe something with a piston or heaven forbid the crank shaft?

any help would save what hair i have left..

 

i remember hearing the vid of you starting it the first time on CF and thinking that it didn't sound right. i remember thinking that it sounded kind of like piston slap or something bottom end.

just saw your thread on cf, is there anyway you can throw the link for that vid up again?



and i'm trying to figure out what kind of engine speed we're talking about on the starter motor, surely it can't be that much. not to mention, it's not firing (like you said you pulled the coil off), and you wouldn't hear a piston slap unless the motor was firing (blowing gas up)

 

hey
the star-up vid sounded bad cause i had the ignition wires crossed and was only firing on 2 cylinders. And then it was running fine. i have never heard this noise before (or at least not this bad) but i will throw up the videos that i have.



engine speed with the starter was maybe 60-70 rpm. with a piston slap is there going to be any damage? or is that just something that i need to replace the wrist pins? and should i do all of them as a set or just any that are out of spec?

 

Check your gold pan matey!!!! er, oil pan for gold

 

talked to a guy here at work who is also a mechanic and he said it sounds like a piston bearing. so if something worked loose i could have a some piston slap.

do you think i will find a bolt or shavings in my gold pan?

 

You'll find gold!!! (gold metal shavings)

 

from the brass bearings... gotcha

 

i took the oil pan off... and found several things... like... GOLD!

first off my oil was a murky grey color.. which is most likely from having not replaced the head gasket after removing the head. i thought that with so few miles on it i wouldnt need to replace it... big no-no. but what baffles me is that the new oil has had only about 10-15 minutes run-time. :wtf: why is it so cruddy? could this have led to my bearing failure?

second i found a bunch of bronze/brass/copper shavings.


Third, i checked the tightness of my connecting rod cap nuts, and all of them were tight, but when i checked piston #4 the whole piston rattles on the camshaft... so i think i found the culprit.

do i have to split the cases to find out if the crankshaft bearings are okay? i should be able to tell if the crankshaft has any play in it without taking it out right? i really dont want to take the engine completely apart again, but i would also rather not have this happen again.


i am going to take the head off again, and pull all the pistons out to check the bearings.

any help would be appreciated
thanks
~Chris

 

Ahhyyy matey ders gold in the high seas!!! You could split the case and realize omg matey I spun a bearing bent a rod an blown a crankshaft... Or you could be like **** this, save money time and buy a new a motor. (hint hint) you would have to buy all new rods an bearings an shaft, then put it all back together and hope you did it right when you can just buy a new motor for say 300 bucks

 

so you are saying that it isnt worth it to just replace the one piston bearing?

where can i find an engine that cheap?