I have one. A bunch of us SV Speedway locals bought some, in the hopes of running a spec race. Hobby People had them on sale for $100.00, we couldn't pass up an onroad engine at the price.
However, a couple of our engines didn't fair well. The inside bearing went bad on them. But most of us have our engines running well. They break in fast (4-5 tanks). Out here in Sun Valley (L.A. area) where we broke in our SH engines, the stock turbo plug (SH 8) seems to be too cold. I ended up using a Nova 6 for break in. This engine likes to run hot here, 235 degrees F was the average. Don't think treat this engine will temp wise like a Nova, RB, or Ninja. It likes to run hot.
This engine can't beat any of the $300.00 and up engines. It gets beat on the straight away at SV. But on the inside of the track, it does very well. We found that putting in the conical header (RB mid header for me) really opens up the power on it. Overall, it's a good practice engine.
KO PROPO HELIOS...yeah that's what I have left after leaving RC.