Vibration above 3700 rpm

I've only had this '79 KZ750 a couple months and am still getting to know it and working through issues as I find them.

I'm getting a lot of vibration above 3700 rpm. Especially in the handle bars and the mirrors are shaking so much at that point that everything I see is a blur.

I'm a new rider and admit I really don't know what's normal vibration for a 32 year old bike at that rpm.

If I wanted to reduce this where would I start?

Is this with the bike on the center or side stand? Is it the same when on the road when riding?
All motorcycles have hamonic vibrations affecting mirrors and instruments. Some bikes have been reported that the left rear foot peg puts passengers feet to sleep when out for a ride.

I'd say get the tools out and check engine mounting bolts for correct torque first, then replace if possible the many and various rubber bits for the side covers & other rubber items.

Ozone and sunlight will dry out the rubber pieces like tires,brake lines and the instrument vibration dampners.

I've mostly only noticed it when riding. I thought it might be wind catching the mirrors and windshield, but it happens at any speed if I get up above 3700 rpm.

I'll try it on the stand and see what happens.

Are there any dampers in the handlebar area or triple tree?

They all do that.
My ZRX has a litle vibration a 4K and then goes away.
Try gell grips or you can fill the handle bars with silicone and BB's.

wrench inside tire?

Have you performed a proper vacuum balancing of the cylinders?

Makes a big difference when using small throttle inputs (cruising), at any rpm.

Make sure your wheels, rubber, bearings, brakes are all in tip top shape and not wearing/rubbing funny.

Good luck.

trianglelaguna wrote: wrench inside tire?

:huh: :laugh: :laugh:

as tek said, sync carbs they prolly need it anywhy!

I am probably due for a proper carb sync but it didn't occur to me that would cause this kind of vibration.

I've got a buddy with a manometer. What else do I need to perform a carb sync?

The manual says I need a special carb sync tool. Can it be done without one?

A Manometer is the "Special" Tool. Borrow his, if you can. And check the sync/ balance. Part of every tune-up really. You won't know if they are out, or by how much till you check.

No the manual refers to a different carb adjustment tool. Motion Pro makes an aftermarket one:
www.amazon.com/Motion-Pro-CARB-ADJUSTING...tech-data/B000GTVOGY

That's the one I'm wondering about. How much easier does this make the job and is it worth the $20 for someone like me with just one bike?

Am a little doubtful about sync having much responsibility for vibration oncoming at 3700 rpm and above.

Would concentrate on other possible remedies such as tightening motor mount bolts, etc.

Good Fortune!

i just used a small yet long flat screw driver and a tiny open ended wrench to loosen and tighten the lock nut

will the tool ake it a lttle easier? probly

do u neeeed to has it? nope