I may have the answer to your problem. I assume you are talking U Turn. If you remove the U Turn adjuster knob you will find ball bearings sitting above little holes with springs underneath. Sometimes only 3 balls are fitted. These balls detirmine how stiff the knob is to turn. You can fit another 2 to 3 balls and springs to stop the U Turn winding too easily. You can buy these from NS Dynamics Suspension. Tell them Rodney (Moruya Bicycles) sent you!
I second this could be a reason for the play, tho ive rode without the knob once and it never moved itself. Maybe test this by trapping up the U-Turn knob with a crap load of gaff tape or something.
Something else you could check is the bolt at the base of the Spring leg. If its not tight it could be rotating as you ride.
This means your spring is rotating, therefore changing travel. Ive noticed that when im putting the fork back together after a rebuild if the bolt doesnt bite onto the lower leg but does with the spring, im basically just "U-Turning" the spring, except from the bottom of the fork.
If its not the upper knob, Id say its the lower bolt. If its none of them, then its internal. And take it back for a replacement (spring or whole thing). The only part left would be the spring its self. Something is wrong with it. Such as how it attaches to the knob or to the lower rod thingy. The spring is a pretty simple part, but i could imagine it becoming loose from the knob.
Saying that, i have 4 U Turn Springs (2 for a Pike) and have not experienced this. And i ride my Lyrik aggressively.
Its a Great fork!
Cheers mate, are they only fitted with 3 balls from RS factory, or do LBS's sometimes do this? I assume it's factory as I think it's pretty much plug and play for the LBS? Other than cutting down the steerer.
Ya 3 balls are factory stock. Also has 3 tiny spring under the balls.... dont let them bounce away