Love the strr, what lehner is that?

Lehner
 

The LEHNER is 1950/4 with Kv 3135: far too high.
I bought it with HI-AMP, forced COOLING & 5mm SHAFT.
It's going too quick and i cannot use it on the STRR.
I'm now using neu 1515 1.5 and i will soon try NEU 1515 1y & 2D.
My problem is runtime. With NEU lipos 4S 5000Mah 30c, i hardly
reach 15 min.
Next days with good weather will be test days.
BTW, the MGM, is perfect with all motors. Never had to complain.