Is your young rider quickly outgrowing their YZ85? Do they need more stability and a smoother ride on rough tracks? Upgrading to a big wheel setup is the perfect solution, but finding the right parts can be a challenge.
We’ve done the research for you. This guide reviews the top big wheel conversion kits and crucial replacement parts to ensure your bike is reliable and race-ready.
| Product Image | Product Name | Best For | Check Price |
|---|---|---|---|
 | YC Yier Complete 17-Inch Wheel S | Complete Big Wheel Conversion | Prices |
 | NICHE 85cc Big Bore Cylinder Kit | Engine Power Upgrade | Prices |
 | NICHE Wheel Bearing Spacer and S | Bearing Spacer Replacement | Prices |
 | All Balls Racing Rear Wheel Spac | Rear Wheel Spacer Replacement | Prices |
 | Tusk Complete Wheel Bearing and | Complete Bearing Service | Prices |
 | Caltric Rear Wheel Ball Bearings | Budget Bearing Replacement | Prices |
 | Air Filter Cage Guide Bolt Repai | Air Box Repair | Prices |
 | All Balls Racing Wheel Bearing K | Oem-style Bearing Replacement | Prices |
YC Yier Complete 17-Inch Wheel S
If you’re looking for a complete, no-hassle wheel kit to upgrade your YZ85 to a “Big Wheel” version, the YC Yier Complete 17-Inch Wheel Set is the perfect solution.
The biggest advantage is that everything you need is in the box. For example, it comes pre-laced with heavy-duty spokes and includes the crucial front brake rotor. This means you can bolt it right on without hunting for extra parts, saving you time and hassle during installation.
Beyond the convenience, the build quality is solid for the price, featuring a durable aluminum rim that can handle the rigors of motocross tracks and tough trails. When you combine the complete package with its robust construction, this kit stands out as a fantastic value for riders wanting a straightforward big wheel conversion.
Pros:
- 👍 Comes as a complete set with hubs, spokes, and rim.
- 👍 Includes the necessary front brake rotor for a direct bolt-on.
- 👍 Durable aluminum construction stands up to hard use.
- 👍 Excellent value compared to buying components separately.
Cons:
- 👎 You may still need to purchase a new, longer chain.
- 👎 Bearings and spacers should be checked for perfect fit upon installation.
- 👎 The finish might not be as premium as some higher-priced OEM options.
NICHE 85cc Big Bore Cylinder Kit
This 85cc big bore kit is the perfect upgrade for a rider who has outgrown their YZ85’s stock power and is looking for a serious, bolt-on boost.
The core of this kit is the larger cylinder and piston, which increases the engine’s displacement for more torque and horsepower across the entire RPM range. This means you can pull out of corners harder without constantly needing to be at peak revs, making the bike feel less frantic and easier to control on technical tracks or trails.
Beyond the power, the quality of the materials is a huge plus. The cylinder features a durable Nikasil plating, which is a professional-grade treatment that resists wear far better than a standard iron sleeve. This attention to detail ensures your investment lasts, making it a reliable and strong choice for serious riders.
Pros:
- 👍 Noticeable power and torque increase across all RPMs.
- 👍 High-quality Nikasil plating for superior durability and heat dissipation.
- 👍 A true bolt-on kit that simplifies installation for most mechanics.
- 👍 Provides a competitive edge without the cost of a full engine rebuild.
Cons:
- 👎 Requires proper jetting changes to run optimally, which adds to the setup time.
- 👎 The power gain may be too much for very new or younger riders to handle.
- 👎 Installation is not recommended for absolute beginners without mechanical experience.
NICHE Wheel Bearing Spacer and S
If you’re converting your standard YZ85 into a “big wheel” version, this spacer kit is an absolute must-have for a smooth and safe installation.
The main job of these spacers is to perfectly center your new, larger wheels between the forks and swingarm. This ensures your brakes align correctly and the chain runs straight, preventing premature wear. Without them, your wheel would be off-center, leading to handling issues and potentially damaging your new kit.
Made from high-quality, CNC-machined aluminum, these spacers are built to withstand serious off-road punishment. They are a direct OEM replacement, so you get a perfect fit without any frustrating modifications, making the whole upgrade process straightforward and reliable.
Pros:
- 👍 Ensures perfect wheel alignment for safe handling
- 👍 CNC-machined from durable aluminum for long life
- 👍 Direct OEM fit for a hassle-free installation
- 👍 A critical, affordable part for a successful big wheel conversion
Cons:
- 👎 Requires you to already have or purchase the main big wheel kit components
- 👎 Installation requires basic mechanical knowledge and tools
- 👎 A small but essential part that’s easy to overlook when ordering
All Balls Racing Rear Wheel Spac
If you’re upgrading your YZ85 to a big wheel setup and need to get the chain alignment just right, this All Balls Racing spacer kit is the perfect solution.
The main benefit is getting your rear wheel perfectly centered in the swingarm. This ensures your chain runs straight, which reduces wear on your sprockets and chain. For example, if your wheel is even slightly off, you’ll notice your chain wearing out much faster than it should.
Made from high-quality steel, these spacers are built to handle the abuse of the track and trail. They are a direct OEM replacement, making installation a simple swap that gives you confidence in your bike’s setup. For a reliable and precise fit, this kit is a top-tier choice.
Pros:
- 👍 Ensures perfect chain alignment for reduced wear
- 👍 Durable steel construction built to last
- 👍 Direct OEM fit for a hassle-free installation
- 👍 An essential, reliable component for any big wheel conversion
Cons:
- 👎 Kit may only include spacers, so check if bearings are needed separately
- 👎 Requires proper installation to achieve the desired alignment
Tusk Complete Wheel Bearing and
This Tusk Complete Wheel Bearing and Seal Kit is the perfect solution for any rider tackling a YZ85 big wheel conversion or a standard hub rebuild.
The biggest benefit is that it’s a complete, all-in-one kit. You get precisely the bearings and seals you need for both wheels in a single package, which saves you the hassle of cross-referencing part numbers and buying pieces separately. For example, when you’re in the middle of a rebuild, you won’t have to stop because you’re missing a critical seal for the rear hub.
The components themselves are high-quality and built to last, featuring durable rubber seals that effectively keep grease in and dirt and water out. For a straightforward, reliable bearing replacement that gets you back on the track or trail quickly, this Tusk kit is a remarkably strong and stress-free choice.
Pros:
- 👍 Complete kit with everything you need for both wheels
- 👍 Saves time and hassle by eliminating part number guesswork
- 👍 High-quality, durable bearings and rubber seals
- 👍 Excellent value for a full set of replacement components
Cons:
- 👎 May require a hydraulic press or specialized tools for proper installation
- 👎 Packaging could be simpler, but all the correct parts are included
Caltric Rear Wheel Ball Bearings
If you’re looking for a simple, no-fuss way to get your YZ85 Big Wheel back to smooth, reliable performance, these Caltric bearings are the perfect drop-in solution.
The bearings are pre-greased and ready to install, which is a huge time-saver. Imagine not having to spend an hour packing grease into tiny bearings before you can even start the real work. This means you can get your bike’s rear wheel spinning freely again in a single afternoon, getting you back on the track faster.
Built to be a direct OEM replacement, they offer solid durability for casual and weekend riders. While a pro racer might need premium-priced bearings, Caltric provides excellent value and dependable performance for most riding conditions, making them a very smart and affordable choice for keeping your bike in top shape.
Pros:
- 👍 Pre-greased and ready for a quick, easy installation.
- 👍 Excellent value, offering reliable performance without the high cost.
- 👍 Perfect direct fit for a hassle-free replacement process.
- 👍 Durable enough for most motocross and trail riding conditions.
Cons:
- 👎 May not last as long as top-tier, professional-grade bearings under extreme racing conditions.
- 👎 The included grease is decent, but some riders may prefer to use their own high-performance brand.
Air Filter Cage Guide Bolt Repai
This guide bolt repair is the perfect solution for any YZ85 Big Wheel owner who’s ever struggled with a stripped or damaged air filter cage bolt.
The main benefit is its simple, permanent fix for a common headache. Instead of wrestling with a damaged thread or trying to re-tap the engine case, this kit gives you everything you need to install a new, durable threaded insert. For example, if your old bolt is seized and the head snaps off, this repair kit lets you restore the mounting point so your air filter seals securely again.
Beyond the core repair, the kit is impressively complete. It comes with a high-quality tap, a new threaded insert, and a robust new bolt, ensuring a perfect fit and long-lasting durability. The included instructions are clear, making this a job most riders can confidently tackle in their own garage without special tools.
Pros:
- 👍 Provides a permanent, heavy-duty fix for a stripped thread.
- 👍 Comes as a complete kit with all necessary components.
- 👍 Saves significant money compared to more complex engine case repairs.
- 👍 Straightforward process that most home mechanics can handle.
Cons:
- 👎 Requires careful drilling and tapping, which can be intimidating for a first-timer.
- 👎 It’s a specific repair part, so you only need it if your original bolt housing is damaged.
All Balls Racing Wheel Bearing K
If you’re tackling a YZ85 big wheel conversion and want to avoid the hassle of chasing down individual parts, the All Balls Racing Wheel Bearing Kit is the perfect solution for you.
The main benefit is having every single seal and bearing you need in one box. This saves you from the frustration of ordering the wrong part or forgetting a crucial seal. For example, when you’re deep into the install, you won’t have to stop your project just to hunt down a missing inner collar.
Beyond the convenience, the quality is solid. The bearings are well-sealed to keep out grime and water, which is vital for longevity on a bike that sees mud and track time. For a straightforward, reliable kit that gets your big wheel build rolling smoothly, this is a fantastic and trustworthy choice.
Pros:
- 👍 Includes every bearing and seal required for the job.
- 👍 Saves significant time and prevents ordering mistakes.
- 👍 Good quality seals help extend bearing life.
- 👍 Excellent value compared to buying components individually.
Cons:
- 👎 You’ll still need a quality grease to pack the bearings.
- 👎 Installation requires the correct tools and some mechanical know-how.
- 👎 The kit is so complete it might include parts you won’t use if your old ones are still good.
Buyer’s Guide: 3 Key Factors to Consider
Durability & Construction
Look for kits made from high-grade aluminum or chromoly steel. These materials offer the best balance of strength and weight savings, crucial for withstanding the hard landings and rough terrain that come with motocross. Don’t just go for the cheapest option; a slightly higher investment upfront can save you from cracked parts and costly repairs down the line.
Completeness of the Kit
A true “big wheel” conversion requires more than just larger rims. Ensure the kit you’re considering includes the longer swingarm and the correct chain guide to maintain proper geometry and chain tension. Using a standard swingarm with big wheels can negatively affect handling and suspension performance, defeating the purpose of the upgrade.
Price vs. Performance
While bolt-on wheel and tire sets exist, a full conversion kit is the proper way to achieve the intended benefits. Consider your budget against the performance gain. A full kit from a reputable brand is a significant investment but delivers a complete, race-ready package with predictable handling. A partial kit might save money initially but could lead to handling quirks.
Frequently Asked Questions
Q1: What is the main benefit of a YZ85 big wheel kit?
A1: The primary benefit is improved stability and traction, especially for taller or growing riders. The larger wheels roll over bumps and ruts more easily, reducing fatigue and boosting confidence, which makes the bike feel more planted and manageable on various tracks.
Q2: Will a big wheel kit make my YZ85 slower?
A2: It can slightly change the final gearing, making each gear feel a bit taller. Many riders don’t notice a significant power loss, and any minor change can be easily corrected by adjusting the sprocket sizes to get your snap and acceleration back to where you want it.
Q3: Is the installation difficult? Can I do it myself?
A3: If you’re comfortable with basic motorcycle mechanics (like changing a rear wheel and adjusting a chain), you can likely handle it. The most complex part is often mounting and balancing the new tires. If you’re unsure, having a professional mechanic do the installation ensures everything is set up correctly and safely.
Q4: Does this conversion affect the bike’s suspension?
A4: Yes, it raises the bike’s ride height. You will need to adjust your sag and may need to re-spring or re-valve your suspension to account for the new geometry and the likely increased weight of the rider this kit is intended for. Proper suspension setup is key to making the kit work well.
Q5: Can I switch back to the stock wheels easily?
A5: Absolutely. That’s one of the great advantages of a kit versus buying a dedicated Big Wheel model. You can swap the entire setup back to stock in a matter of an hour or two, giving you incredible flexibility depending on the track, conditions, or if you plan to sell the bike.
Final Verdict: Which One Should You Buy?
For 2025, a complete YZ85 big wheel conversion kit is a transformative upgrade for the taller, aspiring young rider. It expertly bridges the gap between a standard mini and a full-size bike, offering the stability and control needed to build skills confidently. If your rider has outgrown the stock setup but isn’t ready for a heavier 125cc, this is the definitive solution to extend the life and performance of their YZ85.
Pros:
-
👍 Converts the YZ85 into a more stable and confidence-inspiring machine for taller riders.
👍 Provides better traction and roll-over ability on rough tracks, reducing rider fatigue.
👍 A cost-effective way to “grow” with the bike instead of purchasing a new one.
👍 Typically allows for an easy swap back to stock wheels if desired.
Cons:
-
👎 Represents a significant financial investment on top of the bike’s initial cost.
👎 Requires suspension adjustments and potentially new springs to handle the revised geometry.
👎 Can slightly alter the bike’s peppy power delivery, though this is easily corrected with gearing.