I see no reason other then some mechanical issue that would cause this. The bike SHOULD track straight and true. I run my 80 KZ1000 80+ mph all the time with either very light grip and have removed my hands from the bars.....no issues.

I say start with the bearings.

 

I see no reason other then some mechanical issue that would cause this. The bike SHOULD track straight and true. I run my 80 KZ1000 80+ mph all the time with either very light grip and have removed my hands from the bars.....no issues.

I say start with the bearings.

+1
I exceed 90-100 frequently w/o any problems. If you don't have needle bearings in your steering head it would make a nice upgrade.

 

Tire pressure,condition of front tire(no cupping),swing arm bushing/bearing condition, rear shock condition, and no cracks in frame welds.

 

all great suggestions i am checking them all out now ill post the bike up here soon for people to look at.

 

You might want to check for a sticking front caliper and or warped disc too. Along with the front wheel bearings. If one is tight it can cause feedback.

 

Tires are often the culprit - check tire wear and tire pressure. More than this, many brands and combinations of tires do not work well. The front tire should be a ribbed or semi-ribbed design.

Check wheel alignment - DO NOT rely on the chain adjuster marks. Physically align the wheels - the easy way is get someone to hold the bike upright and get down behind the bike and visually look down both sides of the rear tire. If you see the front wheel, adjust to correct.

Check wheel bearings - wheels should turn freely without any rumbling noise from the bearings
Check steering stem bearings - with the front wheel off the ground, the steering should not be notchy or overly loose.
Check swing arm bearings and regrease with a grease gun
Check for fork seal leaks. If leaking you will have uneven pressure in the forks and this can cause a major ride issue.
Check rear shocks. If the damping fluid had leaked out of one or both, you need to replace them
Check the wheels for straightness - they may be cast wheels, but they can still get bent.

 

Yes, a slightly bent wheel can be the culprit. I just changed out my front wheel for the same problems that you are having. It was most apparent when slowing down. Your bike should be smooth even at top speed.

Also tire pressure can make a big difference. Jeff Saunders pretty much covered it all. Good luck.