I'll tell you now - you will have some major issues using the 1200W on that setup (ezip I assume, with the flip/flop hub). Its a 14 tooth freewheel - right? The easiest way for you to use this is to get a 25H pitch sprocket with a LOT of teeth + a freewheel - and a 25H sprocket with very few teeth for your motor.
3223 rpm (motor) 8T & 14T = 1.75:1 reduction = 1841.715 Rpm - in a 26" wheel (circumference = 2068mm assuming 26 X 1 3/8 tyre) - = ~2m per revolution = 3.6 Kilometres per minute = 216Kph. Yep, its not going to happen. You will smoke the motor or controller.
Cheap solution - get a 80 tooth 25H sprocket + matching freewheel from here... ($29 - comes with bonus wheel
http://secure.oatleyelectronics.com//product_info.php?cPath=94&products_id=810&osCsid=a1472f3da2c6bc94f74b220e3a7dd02b
Along with a 25H chain...
http://secure.oatleyelectronics.com//product_info.php?cPath=94&products_id=670&osCsid=a1472f3da2c6bc94f74b220e3a7dd02b
And a small 25H sprocket that supports a 12mm shaft. A 16T would do it well (with adequate meat for the hub), 13 is doable with the hub being bored to suit on a lathe.
http://www.smallparts.com.au/store/partslist/sprocketsrollerchainmetal/chainandsprockets/all/21/3/
Assuming a 13T sprocket to 80T reduction, this is 6.15:1 reduction, or 524rpm - more manageable - BUT - still damn fast - 1.048K per sec = 62Kph top speed. Possible. Good top speed, no bottom end though.
They do work well when you run them with extra reduction, through the gears. The standard reduction (on a cyclone setup) is 8 (motor) to 44 (chainwheel) - this gives a reduction of 1:5.5 = 586 rpm at the chainring. This is impossible to match by any human (top cadence for an athlete wont pass about 120 rpm).
From the chainring to the second chainring (which drives the cluster) 44T to 24T = 1.83:1 = 320 rpm
Assuming a decent cassette (12-34 cassette) - this equates to 1.416:1 Low gear = 225 rpm = 27 Kph and 1:2 High gear = 640 rpm = 76Kph
Your ultimate reduction range is 14.32:1 Low - 5.03:1 High. You will not get that comfortably in a single stage reduction - Assuming you wanted hill-climbing and a top speed of 45Kph (4500m / 60 / 2 = 375 rpm) and wanted to keep a single stage reduction and the stock 8T motor pulley with a 12.7mm pitch (bike chain).
This is a reduction of 8.6:1 - you would need a 70 tooth 12.7mm sprocket. This is 284mm in diameter - not small!
This is the reason most people run the internal gearbox cyclone setups - for your application, it would be ideal - they run a 9.3:1 gearbox already, so you have an output RPM of 270 rpm on a 14T sprocket. Fit your hub with a 22T freewheel (or 22T fixie - the motor has a freewheel) 1.57:1 = 172rpm = 20 Kph, or a 18T to get 1.286:1 = 210 rpm = 25Kph, or 16T 1.143:1 = 236 rpm = 28 Kph, or 14T to get 1:1 32Kph, or gear up the motor freewheel. The maths is easy.
If you want ~50 Kph = 417 rpm you would need 417/270 = 1:1.54 If your hub has a 14T (1) then your motor needs a 14 X 1.54T sprocket - 21.56 = 22 tooth.
A 22 will give you a no-load speed of 22:14 = 1:1.57 = 1.57 X 270 = 423 rpm = 50.868 Kph. Pretty much spot on.