Diagnosis? 1993 - Knocking / Clunking

[Eli_Z]

Just got my first CB750.  Love the thing, rides like a dream but I started having this problem just this week:

After riding on the highway for a while at 5.5 to 6k RPMs, for maybe 20 - 25 minutes I get off the highway and am back to the surface roads.  I slow down for red lights / traffic.  If I slow down enough to coast in 1st or 2nd gear (or stop at a traffic light) when I again accelerate I get a very unfortunate clunking sound that lasts for a few seconds.

It sounds similar to a clutch plate trying to engage, but the ride is fine.  What I'm reading online - and seeing in diagrams - suggests that it's coming from the vicinity of the cam chain.  It is coming from the left side of the engine, but all the diagram shows where I thought the sound originated is the A.C. generator.  And I doubt it's that.

Anyway, I'm sure someone else has had this problem and maybe even posted about it here... any help?  This is my new baby and I want it to survive a while.

[Re-run]

you know, not many here have  90s cb. I would suggest getting the manual from the repair manuals section.
However, it kinda sounds like a bearing in the tranny might be dying.
It would be really hard to say.
I will see if I can dig up anything.

[Eli_Z]

Thanks man.  I really appreciate it.  It started happening now without even the highway use, though it's much stronger after the highway.

[Re-run]

Have not been able to dig up much so far but a couple questions.
When it clunks, what happens when you pull the clutch in?
Also, what oil are you using? brand and weight.