THE FINAL WORD ON FINAL DRIVE: JULY 2025 ISSUE
GEARING 101
Dear Mr. Know-It-All,
I have been riding off-road motorcycles for a large portion of my 37 years on this planet, but until a couple of years ago I hadn’t done any racing. I now enjoy participating in both motocross and desert racing. Now that I am getting a little faster at both on my 2025 KX450, people keep telling me if I changed my gearing specifically for each event it would help. I have heard to go down a few teeth on the rear sprocket from some people, and others say go up one tooth on the countershaft sprocket. This can be really confusing. Can you give me some expert advice on what is the best way to handle gearing changes, please?
Confused Carl
via [email protected]
Carl, don’t feel bad. Just like a lot of things, when it comes to racing, gearing changes and how to achieve said changes can be confusing for a multitude of reasons. Let’s start off with changes made to the countershaft sprocket (the small sprocket up front). For every tooth you go up or down, it’s like going up or down 2 1/2 teeth on the rear sprocket (some people will argue it’s more like 3 teeth). This will make a drastic difference to your overall gearing versus going up or down 1 tooth on the rear sprocket. Although it does make a noticeable difference, it’s usually used to fine tune the gearing.
MOTOCROSS GEARING
Now, let’s look at some real-world gearing changes that might fit your situation, Carl. Stock gearing on the 2025 KX450 is a 13-tooth countershaft sprocket and 50-tooth rear sprocket. We found on our KX450 test unit that this works pretty well for most motocross and Grand Prix applications. If you’re racing on more of a Supercross-style track, you might want a little more grunt right away, so going up to a 51- or 52-tooth rear sprocket will help you achieve that. Sometimes these changes can require a longer chain. If you’re racing a more wide-open motocross-style track, dropping down a tooth on the rear sprocket to a 49 will give you more top-end speed. Make sure to double-check the chain tension before riding, because you’re probably going to need to tighten it up.
DESERT GEARING
When it comes to desert racing, everything is a lot more wide open, and overall top speed is higher than in motocross. First option is to go down 2 or 3 teeth on the rear to a 47- or 48-tooth sprocket. This may require a shorter chain or at least a healthy amount of adjusting because these sprockets will be smaller in overall diameter. Second option is go up 1 tooth on the countershaft sprocket to 14 teeth. This rarely requires a new chain, because the difference in some of the adjustments might make it necessary. This is also the less expensive option. Front sprockets are usually under 30 dollars whereas a rear sprocket is closer to 100 dollars.
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