Michael, set the needle valves as per the instructions. Around 2 out on the low and 3 out from the bottom on the high end. Get it started and running. You want to run it very rich at first. The ST 90 is ringed so running slobbering rich is good. Let it run in 5 minuit intervals for the first 2 to 3 tankfulls. Cooling completely between runs. Then run it at low to medium rpm's for several more tankfulls slobbering rich. For the next 2 to 4 tank fulls start to lean it out. Untill you get it running decent. You may need to work the low speed needle some here. Remember, the engine runs on the low speed needle till after half to 2/3rds throttle. after this proceedure it should be ok to fly as long as you keep it rich. Ringed engines usually take quite a while to brak in. Don't be surprized if it takes a gallon or more to be fully broken in.

Just take your time. Break it in accordeing to the instructions. My suggestions are guidelines, not holey writ. The ST will treat you well. Mine have, good luck with your ST.

Mark Shuman