Had two MDS one a .40 & the other a .48 I believe. Never could get them to rum properly. They were broken in on a test stand (Per dave Gereke's instructions) . Poor transition, & very difficult to adjust. Our local hobby shop stopped handling MDS engines because of all the complaints. I sold mine! I now have 3 Thunder Tiger .46s and they all run great right out of the box. You really only get what you pay for.