MDS engines are no longer made.

My 38s were some of the best throttling engines I have ever owned. I still have one in a fast delta on a mini pipe and it hauls.

The 40s are variable most are Ok once they are run in and the carb is set. N.B. The factory settings are only approx. every MDS that has been through my hands has needed setting up.

My 68 was great and the 148s I had in 3D models were ultra reliable WHEN RUN IN! They need at least an hour and like 5%.

You will get lots of negative comments on MDS but I liked mine.