On Monday, May 28, 2018 at 6:25:23 AM UTC-7, wrote:
I'd look for anything causing drag on the right wing, could be loose aileron gap tape where the leading edge is forced up under air loads or poorly seated spoiler on the right wing. As noted, right turn has nothing to do with zero ailerons or stick position. If unable to find the cause, a small aluminum trim tab (bent up) placed on the trailing edge of the right aileron will make the aileron fly slightly down and counteract the right turning tendency...........but this remedy will add some drag!
Hope this helps,
JJ

I think JJ's answer is most likely to be correct. I had this symptom on my ASW20 and everything looked fine until I did winter maintenance to polish the wings and replace gap tape. I discovered one lower gap tape had come partially unglued and lifted a little in flight, acting like a little flap. Replacing the tape with fresh cured the problem.

Mike