You could try a Neu 1512 series...they aren't cheap, but, they are the best electric motors available...period. I run a 1512 1YF ( 1900kv ) in my mbx-5 shown here...
It runs cool and it is extremely efficient....on 4s it v/fast. On 5s it is silly fast. If you jump up to 5s, you will want a different esc than a mm esc.
1. MBX-6 T8 1900KV, RX8 ON 4S
2. MBX-5T 1520, MMM ON 5S
3. MBX-5 ONROAD CONVERSION 1515, MMM ON 5S
4. MRX-3 ON ROAD CONVERSION 1512, MMM ON 6S
5. TEN T 2650 T8, MMP ON 3S