Spears Racing's 415 drive chain conversion kit is for both the Kawasaki EX250/300 Ninja and the Yamaha YZF R3 2015+. This kit will reduce your unsprung weight/rotational mass by over 3lbs.

Spears Racing 415 Drive chain kit is used by several WSS300 teams as well as hundreds of race teams around the world.

Since the inception of this amazing product Spears Racing riders have been able to set several track records along with winning several class championships and National #1 plates.



This kit comes standard with an 18t front sprocket and is available with 50,51,52,53,54,55,56,57, 58,59 and 60 tooth rear sprockets. 


When making your choice for the Yamaha R-3you can go with the 18t/55t (3.05) this will be the closest to the OEM gear ratio of 3.07 (14/43). 


When making your choice for the Kawasaki EX300 you can go with the 18t/54t (3.00) this will be the closest to the OEM gear ratio of 3.00 (14/42). 


*** 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 need not to worry about it being " True to the alignment" of your chain and front sprocket (no wobble). 


The drive chain is a DID415ERZ (exclusive race chain) and has a tensile strength of 4,540 and weighs 2.09 lbs./948 Gms. for the Yamaha R-3 and 1.81 lbs./821 Gms. for both the Kawasaki EX250/300cc.


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 following is a Gear Ratio guide:


18/50t - 2.77                         18/56t – 3.11

18/51t - 2.83                         18/57t – 3.16
18/52t - 2.88                         18/58t – 3.22

18/53t- 2.94                          18/59t - 3.27
18/54t – 3.0                           18/60t – 3.33
18/55t – 3.05

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.

 415 Chain Kits

The single best upgrade that any racer can do to their bike.The acceleration of the bike is like a "Superbike" off the corner is amazing.

Jeff Tigert #91 Multi Championship winner 

2015 Pikes Peak International Hill Climb Overall Champion

 Luke Hopkins #26 WSS300 Racer


              I  Love the 415 conversion.

 Compared to the stock setup, the Spears Racing   415 kit allows me to really drive out of the   corners more quickly than stock. I think it is one

 of our best performances per dollar upgrades. One   spin of the rear wheel after installation tells the   whole story. 

  Marc Edwards AFM # 265 Multi class Champion.