Nasty Vibration 4200-4500 rpm

Hi KZ Heads,
I just spent over an hour sarching through the forum and could not find the specific answer to my problem there.
I have a 1980 KZ 1000 E2 (Shafty) and she is runnung well except I have a pretty severe vibration between 4200 and 4500 rpm.
Every thing runs smoth below 4200 and above 4500 (of couse 4200 is right around cruising speed)It appears to have developed over time and is worsening.

Everything appears tight and I did a full tune about 1200 miles ago.
Any Ideas??

check your gas tank mounting bolt, it should be tiiiiight!

Either your pulling my leg or I;m about to flaunt by ignorance again.
What's a gas tank bolt? Mine just sits on rubber bushings.
PS This really feels like engine vibration,

To me it sounds like either the ignition timing is off or a cylinder or two is loosing compression and not doing their job at certain rpms. check your ignition first and see.

kzwolfsr wrote:

To me it sounds like either the ignition timing is off or a cylinder or two is loosing compression and not doing their job at certain rpms. check your ignition first and see.

Thanks for the reply kzwolfsr,
I need to check my manual, but I have the solid sate points & am not sure if timeing is even adjustable.
This weekend I will check compression, re-sinc my carbs and color-tune the mixture. Probably need to check valves while I'm at it. I'ts been less than a year but I'm a daily rider now so wear and tear etc.
I thought it was weird that I'm only noticing it (vibration)through a very narrow power band, but I guess I'll eliminate the basic stuff and go from there.
Thanks

OldtimeRnR wrote:
This weekend I will check compression, re-sinc my carbs and color-tune the mixture. [/quote]

Oh, do you like your color-tune? I've been thinking of picking one up.

does it vibrate when you rev it up in neutral?

Rickman wrote:

OldtimeRnR wrote:
Oh, do you like your color-tune? I've been thinking of picking one up.

Sorry I'm slow to get back pulled a long day.
Yea I love the color tube, It takes a great deal of guess work out of getting your mixture just right. To see really well you need to do it at night or put a blanket over you, but short of buying expensive anylizers or paying someone who has one, it's the bomb baby!

wireman wrote:

does it vibrate when you rev it up in neutral?

Not as badly but it's there. More noticable under load but through all gears at all speeds. 42-45000 rpm??:blink:
If anyone has any more ideas before I tear into tommorow I'd be much obliged. sp?

Does anyone with a shaft drive know if shaft vibration is limited to rpm like that?

Don't mind the wrenching but it's nice to know which bolt to turn.