Adjusting Rear preload

[Bubbleswing]

Is there an easy way to adjust the rear shock pre-load on my California Sidecar 1500 Sport Trike? I have tried to adjust it but can't get at the adjuster to move it. It's our first trike, so I'm new at this. Even with the rear end jacked up I can't get at the adjuster to turn it. Thanks in advance!!
P.S. Loving the trike! Wish I would've done this 20 years ago!!

 

[Mick]

Sometimes you have to spray some oil between the lower collar and shock so it soaks between the shock and the collar and then let it set awhile. They get dirt and grit and water in there so you have to give it a little help ocassionally.