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I have set the chain to 1 inch slack middle of bottom run but it clangs on the chain guard it seems too much slack .....or have I missed something?

Is that 1" total? Doesn't sound enough to me, unless you are talking suspension compressed.
Questions are:
Correct length rear shocks?
Standard gearing?
Loaded or unloaded suspension?

Too tight can give the gearbox output bearing a very hard time. Conversely, too loose can cause wear on the swinging arm pivot - this is exacerbated if the shocks are too long.

Me? OK, not K1's, but the geometry is almost identical,
I set the chain tension where I think it should be then lean over the bike to compress the springs to check it still has around 20-25mm total up/down at worst case.

Hope this helps
George

Thank you ......its all standard ...so I will try leaning it over of the stand and check .

Have you checked for tight spots?

You could have 25mm at a tight spot and 40mm at a slack spot.

I have seen some awful chain wear on swinging arms where the chain crosses to the front sprocket.