Boom Vader (Grom Clone) Front Sprocket Upgrade Considerations.

I was unimpressed when I tested my Boom Vader’s top speed with the stock setup( Stock Boom Vader’s Top Speed Test ). I expected more speed, but I didn’t get it, so I figured I would change this Grom Clone’s gearing and be off with it. However, some front sprocket upgrade considerations need to be addressed.

My goal is more top-end speed for my new motorcycle, and without changing the engine, I have to tune the gearing to give up low-end torque to obtain some top-end speed. 

But first, some questions I found in forums and what my little mind ran with when thinking about motorcycle sprocket changes.

Can I Increase My Sprocket Speed?

Well… I wish. The Boom Vader has a red-line on the tachometer starting at about 8000 rpm range. I was doing speed tests maxing out the engine RPMs. So without risking engine damage, I could not increase the engine RPMs, so I could not increase the speed of the front sprocket.

What Does Changing The Front Sprocket On A Motorcycle Do?

The front sprocket is directly coupled to the engine, and its size can control how much chain is moved per rpm. So changing the size of the sprocket can change the number of chain links delivered to the rear wheel for every engine evolution.

How Does Front Sprocket Size Affect Speed?

If you increase the size of the front sprocket, more links of the chain are delivered to the rear wheel. This increase means more displacement of the chain, which can be translated to more rear wheel revolutions. Therefore an increase in the motorcycle speed.

How Does Front Sprocket Size Affect Torque?

The front sprocket size can affect the torque transmitted to the rear motorcycle wheel, and a smaller front sprocket transfers fewer links to the rear wheel. Still, it leverages the engine torque, increasing the torque felt in the rear wheel—a benefit for accelerating or climbing with the motorcycle.

Is It Better To Change The Front Sprocket Or Rear Sprocket?

The front sprocket on the Boom Vader is small, a 14 tooth, and I am looking to increase it to the max size recommended a 17 tooth. With only a few teeth differences, I am told I can keep my stock chain for now. Move the rear motorcycle wheel forward to compensate for the larger front sprocket—fewer things to change and keep this upgrade cheaper.

Can You Change Just The Front Sprocket?

The front and rear sprockets can be changed at different times, or one left alone while the other is upgraded. My goal is to increase the top speed of the Boom Vader but minimize how much torque I lose in the process.  

Grom Clones aren’t known for their torque or their horsepower. Even if the front sprocket can chain with each rpm, increasing speed requires torque to accelerate higher and higher. 

Hoping a small change, the front sprocket is enough to increase the overall motorcycle speed while retaining the ability to accelerate from a stop to the new top speed.

When Should I Replace My Front Sprocket?

I believe my less-than-happy high-speed test of my Boom Vader requires me to change the front sprocket. At this time, I am not planning on increasing the size of the engine, so this is the fastest upgrade I can do to try and improve the overall motorcycle’s top speed.

What Sprocket Is The Best For Speed?

Quick FB group searches and forum searches result in the largest front sprocket that can go on a Grom Clone without modifying the front gear housing, which is a 17 tooth front sprocket. This upgrade is a good jump from the stock front sprocket, a 14 tooth sprocket, so I should see an increase in speed.

What Is The Biggest Sprocket?

Without modifying the sprocket, the biggest sprocket you can upgrade a Grom Clone to without modifying the sprocket cover is a 17 tooth front sprocket.

Some people have gone without the stock sprocket cover, modifying it, or bought an aftermarket sprocket cover and a larger front sprocket.  

I am trying the 17 tooth front sprocket first in my Boom Vader, and if I want to gear the motorcycle even higher, I can make adjustments to the rear sprocket.

What Sprocket Is The Best For Wheelies?

Not that I do many wheelies, or at least intentionally, but more torque is needed to accelerate the rear of the motorcycle to lift the front, so a smaller sprocket will give the torque necessary to do wheelies easier.

What Is Tall Gearing Motorcycle?

You set up the motorcycle gearing to operate better at higher speeds, often sacrificing torque and acceleration.  

I plan to increase the top speed of the Boom Vader but at the cost of acceleration. :/

Will I Get Less Low-End Torque On My Motorcycle?

By increasing the size of the front sprocket, I will lose some leverage it had in moving the rear sprocket against resistance. This sprocket increase will result in slower acceleration and less climbing torque for the motorcycle.  

I am experimenting here, but I feel the 17 tooth is the max size front sprocket. I can go on my Boom Vader without changing the sprocket housing. If I don’t like the changes the front sprocket upgrade gives me, I can go down to the 16 tooth sprocket, or even the 15 tooth sprocket, to recover torque and regain some acceleration in the Grom Clone.

Does Changing Sprockets Affect The Speedometer?

The Boom Vader, like most Grom Clones, has a speeds sensor attached to the front wheel axle. So changing the sprockets will not affect how speed is sensed on the Boom Vader.

Some motorcycles have speed sensors attached to the engine and measure the bike’s speed based on the engine RPMs. You are changing the number of rear-wheel revolutions per engine RPM by changing gearing. So sprocket changes here might require re-calibration of the motorcycle’s speedometer.

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These are all considerations to keep in mind when changing the gearing on a motorcycle. The Boom Vader doesn’t have much power or torque to work with, so a delicate balance will need to be made to maximize the fun this little Grom Clone will bring me.

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Check For Current 17T Motorcycle Front Sprocket Prices.

As I said, Grom Clone parts are cheap, so going with the 17 tooth front sprocket for now(see what I ordered above), and I will change it if I don’t get the results I want. Check back, and we’ll see how this upgrade works out for me.

Click To See My Recommended

Boom Vader Gen 2 Upgrades

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Motorcycle Sprocket Additional Reading

For more reading, you can read how changing the sprockets on my TaoTao TBR7 worked out, transforming the dual-sport motorcycle into a street motorcycle for me.

• Thoughts On Upgrading Rear Sprocket Of My TBR7.
• TBR7 Rear Sprocket and Studs Upgrade.
• TBR7 Upgrade: Front Sprocket Change.

Or read more about chain drives in general: https://en.wikipedia.org/wiki/Chain_drive