DH Enterprises in Lawndale, California built engines designed by Dale Herbrandson for ULM.

-They were based on single-cylinder Stihl chainsaw engines. He made a two-stroke, two-cylinder Dyad engine that gave 20 hp at 6,000 rpm, between 1975 and 1980.

From Appendix A2/6: These engines were built in the RPV Group by RPV Engine Search (AGARD), from Lawndale, California.

-It is a horizontally-opposed two-cylinder, two-stroke engine giving 18 HP at 6,500 rpm.

-Although certain comments hesitate to classify it as a serial production engine. It was based on the Stihl 090 single-cylinder chainsaw engine.