Clunking noice when i shift

[sam salk]

Hi All-

I have a 1980 CB 750C.  When i shif i hear a clunking noise coming from the the engine about 80 percent of the time.  It sounds like it is coming from low down in the engine perhaps by the oil pan.  Anyone have any ideas?

Thanks,
Sam

[sam salk]

sorry i spelled noise wrong.

[Re-run]

Any particular gear or speed or does it not really matter?
I dont know the dohc bikes that well but I would look at the primary chains, if you have them?, they might be loose.
How many miles to do you have? How long have you had the bike? I ask as the shift dogs might be worn out, especially if there has been some powershifting going on.