On August 25, 1998, approximately 1915 Pacific daylight time, an experimental BD-4, N91LJ, registered to and operated by the second pilot as a 14 CFR Part 91 instructional flight, ground-looped during the landing roll on runway 33 at Crest Airpark, Kent, Washington. Visual meteorological conditions prevailed and no flight plan was filed. The airplane was substantially damaged. Both the flight instructor and commercial pilot were uninjured. The flight originated from Crest Airpark for the local flight. During a telephone interview and subsequent written statement, the flight instructor reported that this flight was the first in a series of ten flights to check out the commercial pilot in the aircraft, and to prepare for his flight review. The flight instructor stated that a normal wheel-landing was made to runway 33 with the second pilot following on the controls. During the roll out, the airplane began to veer to the left. The flight instructor stated that he called out "no brakes" to the commercial pilot with the intention of no brake application until called for, as the right side position does not have brakes available. The flight instructor stated that he corrected the direction or travel back to centerline as the tail wheel was lowered. The airplane remained on the centerline for several hundred feet, then began to veer to the right. The airplane continued to veer to the right and traveled off the runway at approximately mid-field. The airplane subsequently ground-looped before coming to rest on the grassy area between the runway and taxiway. Both pilots reported that there were no mechanical failures or malfunctions with the airplane at the time of the accident.