I have a 2005 kawaski z750s I hear a clunking noise as I pull away and on low speed turns,it appears to come from under the tank,could it be a loose mounting bracket or require chain adjusting

OK, you will need to go back to basics here. 'Clunks' could be several things. Issues like a worn suspension bushing, a worn out ball joint, a perished rubber drive shaft joint or a worn driveshaft carrier bearing.
I'll need a bit more information to help. Sound can travel through solid objects which means the sound might not be coming from under the seat. So when EXACTLY does it 'Clunk'? Is it a single clunk or a regular repeating noise? Does it change with road speed? Does it do it when stopped and idling, only when moving or both? Does it happen just as you pull away and as you slow to a stop? Does it happen as you accelerate/brake hard? When you raise the revs to over 2000 is this at idle or as you drive? All these answers will give clues as to where the issue could be.
Use the comment button below with this information and I'll see if I can help you more.

This scenario could be something as simple as just the exhaust vibrating at a certain time or engine speed and vehicle speed not matching at a point and then the exhaust vibrates against the underside of the floorboard because it is so close to the floor.

Rob, assuming this is a 4X4? Sounds like a bearing. They can vibrate, snap, clunk, all kinds of terrible noises or vibrations.
Axle u joints will also do this. Is it all wheel drive?

is it a clunk or more of a clank?

Have you had the exhaust check for the catalitic converter being clogged. if you are experince low exhaust flow can cause running problems. What can happen is the converter can start to break apart inside and cause restricted air flow.

you may not hear it rattle, or bang on it to hear it loose.

that sounds like you are low on power steering fluid ... when the level gets low then the pump starts to ingest air and that produces a buzzing sound when you turn the wheel .....i would add or change the fluid and check for leaks and mechanical loosness in the under car linkages ...you can have that checked at your next oil change .

could be a ball joint worn out or a spring coil broken

clunking noise front when turning left and does it right also but not as bad 2006 g6 at low speed and goes away as you speed up but always there i have replaced lower control arms both side still there

The belt and pulleys are probably not the cause with the sound you are describing. To me it sounds more mechanical when you say grinding. Have you checked the rear dif?

Check the condition of the sway bar bushings.