SMI doesn't sell directly but you can order it here i.e.:
http://www.mrt-rcshop.de/epages/6307928 ... -S%20MH%22Please note that it's the MH tuned "S" version with loads of torque for small and medium tracks. A "C" version for medium to big tracks like Lostallo or Fiorano is also available and a standard Orcan GT3 engine or the box is available, too, for a more reasonable price in case you don't want to spend the extra money for the MH version. Of course even the standard GT3 is not a budget motor. Together with the Sirio Nemesis and the O.S. Speed V3 the fastest I've ever seen (as MH version).
AND: If you have a problem you can send it to SMI and they will check it for you. They also provide a re-build service if wanted.
GT3-S (MH) Steel main bearing:
http://www.rc-car-news.de/pnews_mag/22_ ... wnews=3281GT3-C (MH) Ceramic main bearing:
http://www.rc-car-news.de/pnews_mag/22_ ... wnews=3282