The big trend here in the Ninja 250R world is Mod First — Sprocket later… Most guys are finding that after adding exhaust, intake, and jetting that the bike is under geared for the new available power. In stock skin, the 2008 Ninja 250R is a gear ratio of 3.21 or 14/45 (14 Tooth Front / Counter shaft sprocket — 45 Tooth Rear / sprocket) and the most common mod now is to replace the front sprocket with a 15 tooth for 15/45 setup or a gear ratio of 3.00 (7% increase in gearing).

As of now the JT Sprocket from Dennis Kirk is the most popular (In fact it’s now sold out) — However after some research I have found a bunch of alternatives. It seems that the late model EX250 and EX500 sprockets fit the 2008, and manufactures are just now updating their fitment lists. So, If you have a favorite sprocket manufacture — Email them for fitment and availability.. And if you have any luck leave us a comment and I’ll try to keep the list updated.

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It has been confirmed that the front sprockets for the previous and next generation Ninja 250r’s are the same. and can be purchased here for about $20. What does this mean? You can +1 the teeth on the front sprocket to help lower the RPM’s and increase the length of each gear.

However, before you do this. You need to recognize that this isn’t going to make your bike “Faster” and can lead to a little engine bog in the lower RPM’s before enough torque is created to turn the additional 7% of leverage needed to turn the larger sprocket. So, this might be a mod better suited for the daily commuter vs. the weekend warrior.