Spears Racing’s 520 drive chain kits is for the Kawasaki EX250/300/400 Ninja and the Yamaha YZF R3 2015+. This kit will reduce your unsprung weight/rotational mass by over two pounds.
These 520 drive chain kits will be the same engineering and machining process that you have come to know with all of the Spears Racing products that have been use to win multiple Race Championships around the World and set several track records along with winning several class championships and National #1 plates.
This Page will allow you to pick the right gearing for your style of riding or track day or racing.You will be able to pick from a 14t or a 15t countershaft(on the engine) and the rears are avalable in the following tooth 40,41,42,43,44,45,46,tooth rear sprockets.
When making your choice for the Yamaha R-3 your OEM gear ratio of 3.07 (14/43).
When making your choice for the Kawasaki EX300 your OEM gear ratio of 3.00 (14/42).
When making your choice for the Kawasaki EX400 your OEM gear ratio of 2.92 (14/41).
*** Just remember that if your looking for more of a drive off the corner you will add a tooth or two.***
The rear sprocket is made from the highest grade aerospace quality 7075-T651 aluminum and weighs (9.64 oz./274g depending on tooth count). It is machined not stamped, this way you don’t have to worry about it being ” True to the alignment” of your chain and front sprocket (no wobble).
The drive chain is a EK racing chain and has a tensile strength of 4,610, and weighs 2.16 lbs./982 Gms. for the Yamaha R-3 and 2.01lbs./913 Gms. for both the Kawasaki EX250/300/400cc.
The steel counter shaft sprocket is drilled to be the lightest steel sprocket on the market (sprocket weights 4.6oz./130 Gms. 18 Tooth)
The large reduction in weight and friction translates to .6/.7 extra HP being transferred to the ground instead of being lost to friction. You also will notice faster acceleration and better handling by reducing the gyroscopic effect of the rotating mass.