Chain adjustment & swing arm question

[mark lander]

I’ve always heard of chains tightening up slightly when after adjustment the axle nut was tightened. Out of all the bikes I’ve owned over the years this has never happened to me except to my 97 B1200. If one looks closely you see the swing arm flexing open ( spreading open at the ends) when loosening the axle nut and of course the reverse when tightening the axle. It’s not just a little bit either. It’s easy to see with the naked eye as you turn the axle nut. I’ve not measured how much it flexes but I’d guess it’s about 3mm.
I’m assuming this it why my chain tightens up so much when the axle nut is tightened down. I’ve done it enough to know how much the chain tightens up and I just compensate when making the chain adjustment. What gives? Am I the only one with a swing arm with a too wide of a wheel opening?

[chevsuz12]

My 97 did it and my 99 does as well.  Guess its just another characteristic of the bandit.

[Red01]

My '01 does it and so does Bobcat's '02.

[ray nielsen]

I use a round rod wedged between the rear end of the axle hole and the adjuster block when tightening the nut -- works wonders and the nut doesn't move the axle.