Novak 3.5 from 4.5 Brushless

[Benh]

I raced a Novak 4.5 brushless this weekend for the first time since i bought it. It didn't seem to run to well, then it cut out. After checking all the connections that are perfect I took it apart. I also took apart my 6.5 motor to see if I could spot any differences and why it was making a funny tapping sound.

My 6.5 has black spacers around the shaft. My 3.5 doesn't. Is this correct?

Has anyone experience this problem before? The rating is 4.5 and the shaft was changed to a 3.5.

Any comments including "you're a noob but...." would be much appreciated!

Many thanks