Quark/Neu No brakes at high speed problem

Hi Guys Just finished my first electric conversion and I love it. My main goal was to destroy the nitros at the local track and as a demonstration unit at big events as we are distributors for quark in Australia.

While in the initial testing I have found that past a certian speed i will have no brakes or no braking power.
So if i manage to hit top speed it will coast untill it drops below a certain speed untill I am able to apply brakes. I have fiddled with the brake settings but nothing seems to change this? Does anyone have any suggestions?


Details

Losi 8ight Pro
Neu 1515 1Y 2200Kv
Quark 125 monster
5 cell 25C Hyperion 5000mah pack
14 tooth pinion currently (smallest I have)

Thanks