challenges with my x6 please advise

[samboneecanada]

Hey all, thanks up front for the help,

I have an x6 on a rough loose track. the straight is about 110' long and it's quite technical
http://video.google.ca/videoplay?docid=-6452076809636839237&hl=en-CA


I have put in the purple losi 84t spur to try in with the stock motor that I have. I'm a bit confused with the whole thing dealing with ratios etc/...

I have access to other size spurs and pinions. I just am a bit lost. I've cooked a few motors already.

Another thing is that I saw a xxxbk2 yesterday that was flying with a 27t stock.

thanks