1515 2Y on 6S???

[suicideneil]

Nay, around 1500-1700kv for 6s lipo is far more common and widely used with great results. I myself run a 2000kv motor on 5s lipo for around 35,000rpms- gearing tall on low voltage with a high kv (relatively speaking) will cause much greater current draw compared to gearing down on higher voltage with the same kv. I would suggest running 6s on your 1515 1y and gearing down before you concider getting a new motor; a 1100kv item would need more like 8-10s to run well from what I've seen- that 30-40k rpm is the magic number to aim for.