Castle Creations 1/18 Sidewinder Micro
 

do I can run a 540 can 27t motor @ 2s on this esc ? geared for around 9-10mph in my 4-5lbs 1.9 scaler ?

No, the 540 motor will stall too easily and kill the ESC.

are you 100% sure ?

Yes, absolutely sure. The only combo that works is a slow/ low geared 55t on 2s, and even then I wouldn't recommend it and Castle won't warranty it.

Too much motor, too little ESC. Get a sidewinder or another 1/10 scale ESC.

The sidewinder 1/10th is a good choice. If you are tight on money look for a used one.