Or, perhaps, they see a "manufacturer" out there, like ZDZ/RCS, BME, DA, or 3W who makes a comparably sized motor (or one slightly larger) that, although more expensive also comes with a 3-year warranty, makes more power, is probably lighter in weight, and can be pulled off the shelf and sent to them, and has readily available spare parts and will be repaired by the "seller".

It's HARD to compete with mass-produced high quality engines from a reputable and established manufacturer, no matter how well you do the work.

personally, if I had the choice between your 30cc motor, and an RCS140 or ZDZ 40, I'd take the RCS/ZDZ, and if BME or DA made a 30-40cc engine, I'd buy theirs first. Why? NOT because yours is based on a "weedy/chainsaw" conversion, but because of the perceived better product and service after the sale and 3-year waranty I'd get from these companies.

It's just VERY hard to compete with that.