I just broke in my 21E yesterday. One thing about it was the break in setting are super rich. When I first started it I would let it idle and it would go through an entire tank of fuel in about 3 minutes just from idling! Also during idling my engine was COLD. I would put my hand on the cooling head and it was barely warm after a whole tank of running. IMO I would turn the HSN in about 1 turn before even starting it. After letting it idle for about 3 tanks I decided it was time to drive it around lightly to finish the break in. So I started it and gave it throttle and it didnt move. It was so rich that the engine couldnt build up enough RPMs to move. All I got was a thick cloud of smoke when I gave it throttle. I put the HSN in about 1.5 turns just so the buggy would drive around. After driving it around for a few minutes my temperatures were where they should've been so it was all good. I think maybe I should of ran the heat cycle method on this engine purely cause the temps weren't where they should have been when idling. Cause when I started to drive it around a bit then the temps went up.

Overall I think the STS 21E is a very good engine. I never had a problem starting it and it ran smooth. I paid $120 for it and it was well worth it.