What size sprockets?

[DamoMotorized]

I am making a motorized bike similar to this one: http://www.youtube.com/watch?v=uruaRsCHvk4, but I am not sure what size sprockets I should use where the 2 red circles are on the picture below. I dont want to buy new sprockets, the sprockets I have now are 14, 17, 20, 24 and 28 teeth. Should I just use the smallest sprocket (14 teeth) on the engine and the biggest sprocket (28 teeth) on the bottom part?

For the other side of the bike i going to keep the 2 sets of sprockets so i will be able to change gears.

Also, i am using a 31cc Ryobi weed wacker engine with clutch.

Thanks.

 

[DamoMotorized]

I dont know if this is going to change much, but I only weigh around 50kg.

 

[DamoMotorized]

Anyone?

 

[DamoMotorized]

I have done some research and thinking and I am pretty sure that im just going to make a friction drive bike. The chain drive method is much more complicated then i thought it would be.

 

[professor]

You need a jackshaft to gear down enough to use that set-up.