A JT Sprockets steel rear sprocket review is something I’ve been looking forward to writing for nearly a year. Before I even picked up the Ultimate Motorcycling Honda CRF300L Rally Project Bike, I had already ordered replacement sprockets from JT Sprockets: a 13-tooth countershaft and 42-tooth rear, both steel. The stock gearing is 14 teeth up front and 40 teeth in the rear.

I knew changing the gearing would alter the bike’s character; I just didn’t know by how much, or whether I’d even like the results. I wanted to wait until I had completed all the power mods before adding the gear ratio changes.

I wanted to tackle the gearing issue one step at a time, so I left the stock 14-tooth countershaft sprocket in place and installed only the 42-tooth rear sprocket.

Installation tip

Installation should have been a simple remove-and-replace, except that I mistakenly tried to turn the hex socket bolt instead of the backing nut. I rounded out one of the soft OEM bolt heads and had to grind the bolt off. Don’t make that mistake.

The sprocket needed no modification or persuasion. It fit exactly as an OEM replacement should. With the larger rear sprocket, the stock chain still fits, though it requires the rear wheel to be adjusted far forward. While that can cause some tire clearance issues with knobbies, I didn’t experience any rubbing with the Tusk Waypoint Adventure tire I am running.

JT Sprockets has been manufacturing replacement and OEM motorcycle sprockets for decades, putting every sprocket through dozens of production stages and rigorous quality-control checks. The company cuts its steel sprockets by hobbing, machining, and drilling to produce accurate tooth profiles and consistent dimensional tolerances. JT states that its rear sprockets are manufactured from C49 high-carbon steel and heat-treated for durability.

Those manufacturing claims were supported by what I found during installation. The machining is clean, the finish is uniform, and the mounting holes aligned perfectly with the Honda hub.

Based on my research, I expected the 42-tooth sprocket to move the engine into a more effective operating range at highway speeds. By turning slightly higher rpm at cruising speed, it spends more time where the engine produces stronger, more usable power.

That proved to be exactly what I experienced. The 42-tooth JT rear sprocket made the CRF300L Rally’s power much easier to use.

New CRF300L Gearing Results

With the stock gearing, maintaining freeway speeds often depended on perfect conditions. A modest headwind, a gentle uphill grade, or simply sitting upright enough to catch more wind would cause the bike to lose momentum. The taller stock gearing left little performance in reserve.

With the JT 42-tooth rear sprocket installed, the difference was immediately noticeable. The Rally now comfortably maintains 73 mph (per GPS) in sixth gear, even on moderate grades. The engine feels more responsive because it is closer to its horsepower peak, giving it enough reserve to handle changing road conditions rather than being overwhelmed.

Off pavement, the benefits are even more apparent. First gear is more useful on technical terrain, and the Rally pulls with noticeably more authority through the gearbox. The motor tractors better through difficult sections, reducing the need for excessive clutch work and making slow-speed riding less fatiguing.

The tradeoff is a reduction in top speed. Gearing down 5% means a commensurate reduction in top speed, depending on conditions. However, the bike maintains highway speeds with greater confidence and requires fewer downshifts on grades or into headwinds. That is a compromise I gladly accept because it makes the CRF300L Rally perform better at the speeds I ride.

Another side effect is speedometer accuracy. The Honda CRF300L Rally measures speed by a crankcase sensor, not the front wheel. So, changing the gearing also affects the speedometer’s accuracy, which is about 4% optimistic in the stock configuration. The 42-tooth sprocket pushes that to about 9% over actual speed.

I’m not going to put the 13-tooth JT Sprockets countershaft sprocket on the bike with the 42-tooth rear sprocket. That would lower the gearing by another 7.7%, which would lift the highway rev count higher than I’d like. However, next time I change the rear tire, I will try the 13-tooth countershaft sprocket with the 40-tooth stock sprocket. The 13/40 combo drops the gearing by 2.6% compared to this 14/42 pairing, and I’m curious how that will feel on- and off-road.

For my riding, the JT Sprockets 42-tooth steel rear sprocket turned out to be the icing on the CRF300L Rally Project Bike’s engine modifications cake for just $31 MSRP. While it doesn’t transform the engine or create horsepower that wasn’t there, it fundamentally changes how accessible that power feels. Whether cruising on flatland freeway, climbing mountain grades, whipping through the twisties, or crawling through rocky trails, the Rally is simply easier and more enjoyable to ride. Sometimes the best performance upgrade isn’t adding power; it’s making better use of the power you already have.