KZ550LTD Vibration

Hi all

First time of posting....here goes...tearing my hair out!!
Recently acquired a 1983 kz550ltd C4... all seems well apart from huge vibration thro' bars and frame when cruising at 50-55 mph at between 4-5000 rpm...If I accelerate thro' the gears at high revs bike gets to 70mph with no vibration. But if I want to go from 45-60 mph while in 5th or 6th gear my jaws literally start shaking. Engine idles smoothly, front wheel has been balanced, brakes have been overhauled, clutch is ok and gearbox is smooth..... a new chain and sprockets have been fitted and front fork seals renewed ....any suggestions?

how fast do you roll on the throttle? Is it really gradual, or a fast blast of gas?

what about the rear tire, balance and condition of both tires, ie no cupping or funny wear marks, swing arm bushigs, stearing head bearings, also the aligment of the chain

Hi pyxen
I wind the throttle pretty quick thro the gears to 70 without vibration.....but when in 4th or 5th I obvoiously turn on the gas slower when accelerating.

Could it be that it's starving for gas when you're trying to do that? Does the engine really grumble on you at that point, like it's bogging?

Does the front wheel wobble, or is it just crazy vibration from the engine? How tight are the engine mount bolts? Are you sure everything is snug in there? Is it rubber mounted? If so - are the bushings still okay?

So many questions!

All seems normal....just changed the fork oil...and that's another story.
I have conflicting methods of measuring oil level, I could use some advice.
Just about to road test....if unsuccessful I think I will fit a new front tyre.
thanks for your help.

While you have the vibration try pulling in the clutch and let the engine go down to idle at 45-60 mph. this may help you figure out if it is the engine or wheel/frame related.

Are carbs in sync?

To ensure the smoothest ride possible for my inherently buzzy 650 I have: new tires/new wheel bearings that I hand packed extra grease into/tightened all my spokes until I hear them "ping" evenly/had my wheels checked for run out and ballanced. My front and back wheels are also aligned with each other. I have different drive sprockets to reduce my highway RPM. I do 4,500 RPM @ 100 KPH.I stuffed a little rubber into my handlebars to avoid cutting the internal wires then I put as many used flat tape backed wheel weights that I could stuff in there. Then I put my bar end weights back on. I also use foam grips amd make sure that my carbs are synchronized, which makes a noticeable difference in handlbar vibration. A guy could also check that all the bolts that mount the engine to the frame are torqued to spec and maybe the steering head assembly needs to be snuged up......My guess is wheels and or bearings, but hell, I'm no mechanic. Just trying to think of things to check buddy.

Double post.

Post edited by: old650, at: 2007/07/09 14:25

Did you check your motor mount bolts?

Hope this is new to you all....lost the last message I was posting.
Good news re-vibration...had the rear wheel balanced and yippee...smooth as silk.
So a big thanks to all who helped with the right answer and to 'harm' for the tip.
My next problem is tyre pressures....bike says 25psi front and 21-28psi rear....garage and tyre company say 34psi front and 38psi rear....all I know is that the higher pressure improves handling but I feel every bump on the road.
What do you think?

Thanks again and what a brill site this is.
Grandadbob