- 1). Refer to the specifications section in your service manual and find the size of the carburetor on your Kawasaki KX80. Most likely, it is a Keihin 18-mm spigot-type. You can verify the actual size by the serial numbers on the side of the carburetor.
- 2). Establish whether you want more mid-range torque for motocross racing or higher top-end speed for open course racing. Change an 18-mm carburetor to a 22-mm carburetor for higher top-end speed. Change to a 20-mm carburetor and go with a larger rear sprocket for motocross.
- 3). Set the ignition timing to the recommended zero degrees TDC (top-dead center). Refer to the specifications in your service manual for the degrees of exhaust valve timing at BBDC (bottom-dead center). Your BBDC should be approximately 93.5 degrees, depending on the year of your motorcycle.
- 4). Retard the timing on your bike between two degrees and four degrees back of TDC to reduce BBDC angle when running the higher rpms at mid-range that are typical with motocross racing. Stay with your bike's stock BBDC timing angle for high-end performance on open courses.
- 5). Count the number of teeth on your rear sprocket. KX80 stock is either a 49-tooth or 54-tooth sprocket, depending on your gearing setup. Some motorcycle shops and dealers set bikes up as ready-made for certain types of riding.
- 6). Ride your KX80 and establish whether the rear sprocket has a tendency for low-end performance or high top-end speed. Stay with the rear sprocket on your motorcycle if your other powerband adjustments have accomplished your goal. Otherwise, go with a 54-tooth sprocket for more low-end torque, or a 49-tooth sprocket for higher top-end speeds.
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