Can anyone help?
I am looking at the primary chain on my X1 ,the manual says adjust to said deflection with the chain at its tightest spot.
Can anyone elaborate on this?
I am thinking that as I am turning the engine over with the spark plugs out and holding the tension with my hand on the rear wheel would this be the "tight spot on the primary chain.
Thanks in advance. Just servicing the beast at the moment.

No, a chain is made from lots of individual plain bearings. These wear at different rates (slightly) and manufacturing tolerances in each may be different. So some parts of the chain may be 'slacker/tighter' than other sections (commonly and mistakenly known as 'stretch'). If you tensioned the chain at a 'slack' section, then the tight part, several inches down the chain would be way too tight.
When checking, don't hold any tension in the chain with the back wheel, let it hang free and check the play in 4 or 5 different places. If you're lucky, you may get the same measurements in each place.

I've not explained this very well, have I?

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If your dreams don't scare you, they are not big enough.

Yes you have...but it might be simpler to just consider that the sprockets may not be perfectly round...

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'98 M2 Razorback, it's a keeper.

I was nearly going insane
well same as the chain and sprockets on my other bike .
Off back to finishing off the service now.
Thanks again for the help hope this could help someone else as its not always obvious in a manual.