Topic: CB750K - how much vibration is "normal"?

[cookindaddy]

I've just had 50 miles on my "new" 78 750K that I installed an engine into that I rebuilt. It was FABULOUS to ride it again!

I notice that there is a vibration in the engine at about 5000 rpm. I don't remember where the peak vibration was in the previous engine, that was last year. Also I have not ridden the bike since last year and my memory for vibration isn't great.

I wouldn't say that it was objectionable but it is noticeable. The mirrors don't have a clear image when I am at this rpm while the rest of the time they do. (Good stiff Honda original mirrors with the thick support post).

It is such that I would prefer to downshift or upshift. It is pretty sharp peak also, from about 4800 to about 5100 rpm.

I realize that this is a pretty subjective question, but I am interested in hearing if you have a point on your rpm curve where you would rather not ride for extended periods? Or perhaps to hear that there is something wrong with my new build because yours is absolutely smooth from zero to 10,000 rpm??

Thanks!

[Gordon]

The harmonic convergence on my 750 is at about 7200 rpm, but I manage to keep it below that most of the time .

Make sure the engine mounts are all tight, and do a thorough tune-up including a carb synch.  That will get your bike about as vibration free as it can be. 

Are you feeling it more through the seat and footpegs or through the handlebars?

[cookindaddy]

Thank you.
I've done the bench sync, but not with the meter (I have the Morgan but haven't used it yet).
I don't know, now that you ask, how I feel it. It seems to just be there. Definitely the handlebars because of the mirror. I will pay more attention tomorrow.
Why do you ask that?
I am sure that the motor mounts are firm.