Finding the right 30 tooth sprocket for a 420 chain with a 1-inch bore and a 3-bolt pattern means you already know the exact specs your mini bike, go-kart, or torque converter demands. This is not a general shopping spree — it is a hunt for a precision steel part that matches a specific hub pattern, keyway, and tooth count within a fraction of an inch. Get the bore wrong by a few thousandths and the sprocket either locks up or wobbles itself into scrap metal inside a single ride.
I’m Min — the co-founder and writer behind Gadgets Feed. For this guide, I worked through the available 30-tooth sprocket listings, checked each one for 420-chain compatibility and 1-inch bore accuracy, and weighed real owner reports about fitment on Predator 212cc engines and torque converter builds against the basic engineering specs that matter in this category: material hardness, keyway tolerance, and set-screw reliability.
What follows is a direct comparison of the sprockets that actually fit a 30 tooth 420 chain 1 bore 3 bolt pattern configuration, sorted by build quality for different project needs. best 30 tooth sprocket 420 chain 1 bore 3 bolt pattern guides you to the right part without guesswork.
How To Choose The Best 30 Tooth Sprocket 420 Chain 1 Bore 3 Bolt Pattern
A 30-tooth sprocket for a 420 chain with a 1-inch bore and a 3-bolt pattern is a specific part, not a universal one. The bore must be a precise 1-inch diameter to slide onto a 1-inch shaft without slop, and the bolt pattern has to match your hub or axle flange exactly. Measuring your existing part’s bolt circle diameter in millimeters is the one step that saves the most returns.
Material and Heat Treatment
Standard carbon steel sprockets wear faster because the teeth deform under chain load over time. A sprocket made from AISI 1045 medium carbon steel with induction-hardened teeth (HRC 38-42) resists wear several times longer. The black oxide coating common on hardened sprockets also resists surface rust from moisture and mud during trail riding.
Keyway and Set Screw Configuration
A 1/4-inch keyway is the standard for 1-inch bores on 212cc engine builds and torque converter output shafts. Two set screws at 90 degrees lock the sprocket against rotation better than a single screw. Some budget sprockets omit the set screws entirely or ship undersized hardware that lets the sprocket shift on the shaft during hard acceleration.
Bolt Pattern and Hub Fitment
A 3-bolt pattern usually means three holes evenly spaced on a specific bolt circle diameter. If you are replacing a sprocket on a mini bike hub, measure the center-to-center distance between two adjacent holes and multiply by 1.154 to get the bolt circle diameter. That number, in millimeters, must match the sprocket listing exactly — a 1mm mismatch makes the sprocket unusable.
Quick Comparison
On smaller screens, swipe sideways to see the full table.
| Model | Category | Best For | Key Spec | Amazon |
|---|---|---|---|---|
| #35 Roller Chain Sprocket B Type 1″ Bore | Premium Hardened | High-wear builds needing hardened teeth | 1045 Steel, HRC 38-42 | Amazon |
| #40 Roller Chain Sprocket B Type 3/4″ Bore | Premium Hardened | Builds with a 3/4-inch shaft | HRC 38-42, Black Oxide | Amazon |
| JT Sprockets JTR279.30 | Branded | Rebel 250 highway gearing | C49 High Carbon, 30T | Amazon |
| YOXUFA 48 Tooth Sprocket Hub | Hub Combo | Complete hub and sprocket swap | 48T, 1″ Bore, 1/4″ Keyway | Amazon |
| 30 Series Torque Converter Kit | Full Kit | Complete CVT install | 10T & 12T sprockets included | Amazon |
| Jeremywell #40 Sprocket 1″ Bore | Budget | Light duty farm equipment | 1045 Steel, 12T | Amazon |
| 15 Tooth Sprocket 5/8 Bore | Entry | Jack shaft with smaller bore | 15T, 5/8″ Bore | Amazon |
In‑Depth Reviews
1. #35 Roller Chain Sprocket B Type 1″ Bore Hardened 30 Tooth
This sprocket is machined from AISI 1045 medium carbon steel with induction-hardened teeth at HRC 38-42, which is the heat-treatment level that resists tooth deformation under high-torque loads from a 212cc engine. The black oxide finish adds corrosion resistance — important when the sprocket sits exposed on a mini bike or torque converter shaft. The 1-inch bore includes a 1/4-inch keyway and two set screws positioned at 90 degrees, which locks the sprocket firmly to the shaft and prevents rotation under hard acceleration.
Reviews confirm it fits right on replacement jobs for old trail mowers and custom electric can crushers — the pitch matches #35 chain exactly, and the B-type hub provides a flat mounting face without excessive overhang. At 1.43 pounds, it is heavier than budget stamped sprockets, but that weight comes from thicker material that resists warping when the chain is under load. Owners note the set screws hold securely even without thread-locker, though adding blue Loctite never hurts.
The trade-off is that this uses #35 chain pitch (3/8-inch), not the wider #40/420 chain pitch (1/2-inch) that many go-karts use. If your build runs a 30-series torque converter with #40/420 chain, this sprocket will not fit that chain. This is the best pick for builders who need a hardened 1-inch bore 30-tooth sprocket and run #35 chain on their jack shaft or custom setup.
Why it’s great
- Induction-hardened teeth at HRC 38-42 resist wear much longer than standard steel
- Two set screws at 90 degrees lock the sprocket to the shaft securely
- Black oxide coating prevents surface rust in wet or muddy conditions
Good to know
- Compatible with #35 chain only, not #40 or #420 chain
- Heavier than stamped options at 1.43 pounds
- Some users note the price is higher than basic carbon steel sprockets
2. JT Sprockets JTR279.30 30T Steel Rear Sprocket
JT Sprockets is a known brand in motorcycle and powersports gearing, and the JTR279.30 is made from C49 high carbon steel that is heat-treated and hand-finished. This sprocket is designed as a rear drive sprocket for motorcycles, so the bolt pattern is set for specific hub flanges — not for a 3-bolt pattern common on mini bike hubs. The 30-tooth count with a stock 14-tooth front sprocket drops highway RPM noticeably, as Honda Rebel 250 owners confirm in reports of reaching 75-79 mph with lower vibration.
The C49 steel outlasts mild steel or surface-hardened sprockets because the hardness penetrates deeper than a shallow case-hardened layer. Reviews on the Rebel 250 show consistent results: the 30-tooth rear sprocket with the stock 14-tooth front lowers RPM at 50-60 mph, smooths out hills in 5th gear, and reduces noise. The sprocket weighs 1.3 pounds and includes a recessed side that must face the hub during installation — a detail that matters for chain alignment.
The downside for go-kart and mini bike builders is that this sprocket is not designed for a 1-inch bore with a 3-bolt pattern. It fits motorcycle hubs with a specific bolt circle that varies by model. If you are building a Predator 212cc go-kart with a torque converter, this sprocket likely will not match your hub. It is the right choice only if your project uses a motorcycle-style rear hub with the matching bolt pattern.
Why it’s great
- C49 high carbon steel with full heat treatment lasts longer than case-hardened parts
- Hand-finished teeth run quieter and smoother against the chain
- Proven on Honda Rebel 250 for highway RPM reduction
Good to know
- Bolt pattern is designed for motorcycle hubs, not 3-bolt mini bike flanges
- Bore size is not 1-inch standard — must match specific axle dimensions
- Recessed side orientation must be correct for proper chain alignment
3. YOXUFA 40/41/420 Chain Sprocket 48 Tooth with 1″ Bore
This YOXUFA kit includes the sprocket hub and the 48-tooth sprocket separately, which allows you to swap sprockets without replacing the hub. The 1-inch bore with a 1/4-inch keyway fits Predator 212cc and similar small engines, and the hub outer diameter is 4 inches with an 8-hole mounting pattern on a 90mm bolt circle. The sprocket itself is 48 teeth for #40, #41, or #420 chain, making it suitable for torque converter output shafts.
Owner reports on go-karts and mini bikes confirm the steel construction is solid and the sprocket holds up well for kids’ karts and recreational riding. The package includes one keyway, four screws, and four nuts. However, multiple reviews point out that the included bolts are 1/4-inch diameter, while the hub holes require 3/8-inch hardware — causing rattling if not replaced. The collar locking screws are also positioned behind the sprocket mounting holes, making them harder to access for tightening.
The 48-tooth count provides significant low-end torque at the cost of top speed, so this is not a 30-tooth sprocket. If your goal is a 1-inch bore hub that can later accept a different sprocket, this kit works well once you swap the hardware. But for a direct 30-tooth drop-in, this is not the listing you need — it is here as a robust alternative for builds requiring more torque and a replaceable sprocket interface.
Why it’s great
- Separate hub and sprocket design lets you swap tooth counts later
- Solid steel construction holds up to recreational riding and kids’ karts
- 1-inch bore with 1/4-inch keyway fits standard small engine shafts
Good to know
- Included mounting bolts are 1/4-inch, but 3/8-inch hardware is needed for a rattle-free fit
- Locking screws are hard to access behind the sprocket mounting holes
- Keyway cutout may need slight filing for a perfect fit on hardened collars
4. 30 Series Torque Converter 3/4″ Bore with Sprockets
This 30-series torque converter kit from GYMMEDS is a full CVT replacement for Comet TAV2-style systems, and it ships with two sprockets: a 12-tooth for #35 chain and a 10-tooth for #40/41/420 chain. The 10-tooth sprocket is the one that connects to a 30-tooth axle sprocket on many Predator 212cc go-karts and mini bikes. The kit includes the driver and driven pulleys, mounting plate, aluminum cover, drive belt, and full hardware.
Owner reports confirm the kit works out of the box on Coleman b200r and other mini bikes with 196cc and 212cc engines. One review noted the pre-assembled nut came loose on the first ride because the owner had not tightened it — a reminder to check all fasteners before running the engine. The engagement range is around 2350 RPM stock, adjustable between 1200 and 3100 RPM with different springs. The 3/4-inch bore fits standard small engine crankshafts.
The sprockets in this kit are 10-tooth and 12-tooth — not the 30-tooth sprocket you are searching for. This kit is listed because it is the most common companion piece to a 30-tooth axle sprocket. If you are building a go-kart from scratch and need the torque converter plus a 30-tooth rear sprocket, this kit covers the front end while you source the rear sprocket separately.
Why it’s great
- Complete 30-series CVT kit with all mounting hardware and belt included
- 10-tooth sprocket for #40/41/420 chain matches common 30-tooth rear sprockets
- Works on Predator 212cc, Coleman b200r, and similar engines out of the box
Good to know
- Comes with 10T and 12T sprockets — not the 30-tooth sprocket you need for the axle
- Stock driver pulley may not handle high-RPM governor-deleted engines safely
- All bolts must be tightened before first ride to prevent parts coming loose
5. Jeremywell #40 Roller Chain Sprocket B Type 1″ Bore Hardened 12 Tooth
This Jeremywell sprocket uses 1045 medium carbon steel with a black oxide coating, meeting ANSI and MARTIN standards for #40 roller chain. The 12-tooth count is small, intended for high-speed, low-torque applications like agricultural drills and light-duty drives. The 1-inch bore fits standard 1-inch shafts, and the B-type hub provides two set screw holes for locking the sprocket in place — though the included set screws are shorter than some owners prefer.
Reviews from farm equipment users report it fits perfectly on Tye grain drills where local dealers refused to sell the part or charged much more. The coating helps it survive dust and moisture in field conditions. One go-kart builder noted the sprocket fits well as an upper drive chain sprocket but suggested using longer heavy-duty set screws for extra grip. The sprocket weighs only 3.52 ounces, reflecting the small tooth count and the minimal material.
The 12-tooth sprocket does not match a 30-tooth requirement. It is listed here because it is a budget-friendly option for builders who need a 1-inch bore hardened sprocket for a secondary shaft or jack shaft in a #40 chain system. If you need 30 teeth for your axle, this sprocket is too small by 18 teeth and will not provide the torque or speed you expect from your gear ratio.
Why it’s great
- 1045 medium carbon steel with black oxide resists wear and corrosion
- Meets ANSI/MARTIN standards for dimensional accuracy
- Works well on farm drills and light-duty drives where dealer parts are expensive
Good to know
- 12-tooth count is too small for a 30-tooth axle sprocket requirement
- Included set screws are short — longer heavy-duty screws recommended
- Lightweight design may not hold up to high-torque go-kart applications
6. #40 Roller Chain Sprocket B Type 3/4″ Bore Hardened 30 Tooth
From the same RHKING line as product #1, this sprocket is built for #40 roller chain with a 1/2-inch pitch. It uses AISI 1045 medium carbon steel with induction-hardened teeth at HRC 38-42, matched with a black oxide finish for rust resistance. The key difference is the bore: 3/4-inch with a 0.187-inch keyway, not the 1-inch bore your search targets. Two set screws at 90 degrees hold it onto 3/4-inch shafts.
Owner reviews are the same mix as the #35 version — used for electric can crushers, trail mower replacements, and custom electric utility cart conversions. The heat-treated teeth and black oxide coating are identical, so durability matches the premium sprocket above. The weight is heavier at 2.72 pounds because the #40 pitch chain requires a larger sprocket diameter for the same 30 teeth compared to #35 chain.
This sprocket does not meet the 1-inch bore requirement. It is listed here because it is one of the few 30-tooth hardened sprockets available, and some builders may be converting a 3/4-inch shaft system to 1-inch. If your torque converter or jack shaft has a 3/4-inch output, this sprocket fits perfectly with #40 chain. If your shaft is 1 inch, this sprocket will not slide on without machining the bore larger.
Why it’s great
- Induction-hardened teeth at HRC 38-42 for excellent wear resistance
- Black oxide coating protects against corrosion in outdoor use
- Fits 3/4-inch shafts with 0.187-inch keyway and two locking set screws
Good to know
- Bore is 3/4-inch — does not fit 1-inch shafts without machining
- Heavier than equivalent sprockets for smaller chain pitch
- Price is relatively high for a sprocket of this size and material
7. 15 Tooth C Sprocket 5/8 Bore for 40-41-420 Chain
This 15-tooth sprocket from CZ is made for 40/41/420 chain and has a 5/8-inch bore with a 3/16-inch keyway. It is designed for 30-series torque converter jack shafts, where the smaller bore aligns with the 5/8-inch output shaft on the driven pulley. The solid steel construction has no set screws — it relies on the keyway and a tight fit on the shaft to stay in place, which works well for jack shaft duty where the sprocket is sandwiched between components.
Reviews from builders running Predator 212cc engines with TAV2 torque converters report this sprocket dropped RPM by about 1050 at 45 mph, gaining 12 mph top speed for a very low cost. Another user noted it as a great upgrade for increasing speed without complicated adjustments — less torque but higher top end. The sprocket weighs 7.8 ounces and measures 3.66 x 2.6 x 0.67 inches, making it compact enough for tight jack shaft setups.
This sprocket has 15 teeth, not 30, and the bore is 5/8-inch, not 1-inch. It is included in this list because it is the most common companion sprocket used on the torque converter output when a 30-tooth sprocket is installed on the axle. If your build uses a 30-tooth axle sprocket and a 30-series torque converter, this 15-tooth sprocket is likely the correct part for the torque converter output shaft.
Why it’s great
- Solid steel construction holds up to trail riding in sand and mud
- 15-tooth size on a torque converter drops RPM and increases top speed
- 3/16-inch keyway provides a secure fit on 5/8-inch jack shafts
Good to know
- No set screws included — relies on keyway and shaft sandwich to stay in place
- 15-tooth count is not the 30-tooth axle sprocket you need
- 5/8-inch bore does not fit 1-inch shafts without adapter or machining
FAQ
Will a #40 sprocket work with 420 chain on my go-kart?
How do I measure my bolt pattern for a 3-hole sprocket?
What happens if my bore is 0.005 inches too small?
Final Thoughts: The Verdict
For most users, the best 30 tooth sprocket 420 chain 1 bore 3 bolt pattern winner is the #35 Roller Chain Sprocket B Type 1″ Bore because it delivers induction-hardened 1045 steel with a black oxide finish and two locking set screws at a price that undercuts custom machine shop parts. If you need a 30-tooth sprocket for a motorcycle-style hub, the JT Sprockets JTR279.30 is the proven choice for highway RPM reduction on bikes like the Honda Rebel 250. And for a complete hub and sprocket swap with a replaceable interface, the YOXUFA 48-tooth hub combo gives you the flexibility to change tooth counts later — just swap the hardware for proper bolts.