Chances are, if you're reading this, you were in the owners group asking about swapping sprockets and someone linked you to this.

We've assembled a few videos that should help explain how changing sprockets affects your performance.

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This is a basic overview. The intention was to help address new owners questions about sprocket swaps since they come up very frequently in the owners groups.

If we were to boil the concept of sprocket changes down to it's absolute simplest; the gears are responsible converting rotations of the engine into rotations of the rear wheel.

Assuming the engine is turning at a constant speed: fewer turns of the rear wheel would represent more power while more turns of the rear wheel would represent less power and more speed.

Lets be real, you're not going to turn your Grom/Monkey into a rocket ship by dropping a tooth in the front, but it will give it a little more power at the expense of a small amount of top speed. Also, if you're going to be attempting these changes as a new owner, you need to be familiar with how to adjust your chain and make sure everything is aligned right since you'll be adjusting the rear wheel during the process of swapping sprockets. We recommend using a chain alignment tool like this one.

Part of the reason people want to swap out their gearing to either a smaller front or larger rear sprocket on these mini-moto's is because the stock gearing simply doesn't allow the engine to make use of its full RPM range. Post after post comes across the forums about changing gearing because the bike just sortof gives up halfway through 4th (5th on the new transmission) gear. Counter-intuitively, if you gear it down a tooth in the front (or up 3 in the back) you'll likely be able to hit higher top speeds, but your RPM's will be higher at those speeds, which is great on low-speed roads with alot of turns, but isn't ideal for long trips at full throttle.

We did receive a question about how sprocket swaps affect fuel mileage. While this isn't something we've done any testing on in regard to sprocket changes, fuel mileage is going to depend on the rpm's you're sustaining at cruising speed. If you're dropping a front sprocket tooth, you'll have to maintain a higher RPM than before to cruise at 50mph than you did previously, and it's likely going to drop your mileage a couple mpg. I feel like the performance boost is absolutely worth it though.

Honda MiniMoto (Grom/Monkey) specific tips:

The 2022+ bikes come with a 15t x 38t sprocket set, Previous generations came with a 15tx34t sprocket set. On older models everyone recommended changing the front sprocket to a 14T, but honda has incorporated that from the factory in the new bikes by making the rear sprocket larger. So, if you see people talking about swapping your front sprocket and you've got a 2022, this common change has basically already been done.

Another thing to remember is that 1 tooth on the front is equal to 3 teeth on the back sprocket. Dropping one tooth in the front is like adding 3 to the back, and vise versa. Going with a smaller sprocket in the front is one of the most popular options simply because it's cheaper to do. Rear sprockets are more expensive, and typically when you up-size the rear sprocket, you'll need a longer (new) chain. The narrower diameter of small front sprockets increase chain wear, but larger sprockets and more chain length will weigh more, so it's really a choose your poison situation. I'm not racing on a track, so I pick reliability/longevity over shaving a few grams.

Don't be tempted to drop your front sprocket down to a 13T or you wont have enough sprocket diameter for the chain to clear the plastic protector plate on the swingarm.

Your speedometer is going to be reading incorrectly if you change sprockets. Some people don't mind an inaccurate speed reading, but this will also affect how your bike logs miles, which can in turn affect your ability to determine when maintenance needs to be performed. Speed correction factor is a percentage of your stock speedometer reading. 12 O'clock labs has done all of the work in providing us a handy calculator where you can plug in a few bits of data and get the percentage that you need to enter in your SpeedoHealer or OPMID gauge. Just as an example, for my 2021 Monkey with 15x37 gearing and Michelin Pilot Pure tires, the speed correction factor I use is 92.3%

To correct your speed, you'll need to either install a SpeedoHealer or replace your gauge altogether. At STL Smallbore, we recommend the OPMID.

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