Motorcycle Repair: 1985 zx600, clutch basket, clutch plates

Question
QUESTION: i am hearing a noise coming from my transmission while the bike is idle , I've changed the clutch and the basket. as was recommended, but the noise is still there! when i turn up the idle the noise goes away, when it's in gear the noise goes away, please help this is my first bike

ANSWER: Steve,

did you use a new or used clutch basket?
Sometimes the rivets are loose on the back.

-When your bike is in gear with the clutch pulled
in, the transmission is not turning. Only
the outer part of the basket is turning
and the clutch plates are not engaging
the transmission shaft yet. So any noise
would not be in the transmission in this case.

-When you have the bike in neutral with
the clutch out, the transmission mainshaft
is turning. If this is when you hear the
noise, it is likely inside the transmission.
It could be a rough bearing or gear or
noise caused by a bent shift fork.
Unfortunately the bottom end of the
engine must be disassembled to fix this.

-When you speed the engine up it just changes
the harmonics of the noise so it
is less noticable.

-you could try some 20W50 oil and see if it
helps.

http://www.cmsnl.com/img/Kawasaki_TRANSMISSION_1985_A1_ZX600-partslist-big-KAE05


---------- FOLLOW-UP ----------

QUESTION: I haven't tried the oil yet but i will give it a shot!, know if i have to change the shift fork or bearing, do i have to take the whole engine apart or does just the bottom end come off,

Answer
Steve,

You will have to remove the engine and
the clutch and shifter parts etc to
split the bottom part of the crankcase.

-You should be able to leave the top end
alone for now. As you disassemble the
engine look for wear on the parts you remove.

-You could partly disassemble it while
in the frame just in case you happen
to find out what is making the noise
before tearing the whole thing apart.

-I strongly recommend using a repair manual
if you decide to go into the transmission.
There are many things that need to be checked
and assembled correctly to avoid problems later.

-you may want to have a shop technician listen to it
and get his opinion on where the noise is located.