heat transferring goo?

[What's_nitro?]

This stuff works great for all of my applications. Good price, too. So far I've used it on my laptop's CPU and GPU, and also my MGM and Sentilon controllers. I've never used a heatsink on a motor but I know the gap that you are talking about, and it would bug me too. The motor is guaranteed to be round, so it's the heatsink clamp that is out of shape. I would try (gently) to reshape it. Thermal paste may not help unless you can eliminate most of that gap.